Risk factors and pattern of metastatic recurrence after endoscopic resection with additional treatment for esophageal cancer.

Although esophageal cancers invading the muscularis mucosa (pT1a-MM) or submucosa (pT1b-SM) after endoscopic resection (ER) are associated with a risk of lymph node metastasis, details of metastatic recurrence after additional treatment remain unknown. We aimed to identify the risk factors for metastatic recurrence and recurrence patterns in patients receiving additional treatment after ER for esophageal cancer. Between 2006 and 2017, patients with pT1a-MM/pT1b-SM esophageal cancer who underwent ER with additional treatment (esophagectomy, chemoradiotherapy [CRT], and radiation therapy) at 21 institutions in Japan were enrolled. We evaluated the risk factors for metastatic recurrence after ER with additional treatment. Subsequently, the rate and pattern (locoregional or distant) of metastatic recurrence were investigated for each additional treatment. Of the 220 patients who received additional treatment, 57, 125, and 38 underwent esophagectomy, CRT, and radiation therapy, respectively. In the multivariate analysis, lymphatic invasion was the sole risk factor for metastatic recurrence after additional treatment (hazard ratio, 3.50; P = 0.029). Although the risk of metastatic recurrence with additional esophagectomy was similar to that with CRT (hazard ratio, 1.01; P = 0.986), the rate of locoregional recurrence tended to be higher with additional esophagectomy (80.0% (4/5) vs. 36.4% (4/11)), leading to a better prognosis in patients with metastatic recurrence after additional esophagectomy than CRT (survival rate, 80.0% (4/5) vs. 9.1% (1/11)). Patients with lymphatic invasion have a high risk of metastatic recurrence after ER with additional treatment for pT1a-MM/pT1b-SM esophageal cancer. Additional esophagectomy may result in a better prognosis after metastatic recurrence.

Regulatory Role of GgaR (YegW) for Glycogen Accumulation in Escherichia coli K-12.

Glycogen, the stored form of glucose, accumulates upon growth arrest in the presence of an excess carbon source in Escherichia coli and other bacteria. Chromatin immunoprecipitation screening for the binding site of a functionally unknown GntR family transcription factor, YegW, revealed that the yegTUV operon was a single target of the E. coli genome. Although none of the genes in the yegTUV operon have a clear function, a previous study suggested their involvement in the production of ADP-glucose (ADPG), a glycogen precursor. Various validation through in vivo and in vitro experiments showed that YegW is a single-target transcription factor that acts as a repressor of yegTUV, with an intracellular concentration of consistently approximately 10 molecules, and senses ADPG as an effector. Further analysis revealed that YegW repressed glycogen accumulation in response to increased glucose concentration, which was not accompanied by changes in the growth phase. In minimal glucose medium, yegW-deficient E. coli promoted glycogen accumulation, at the expense of poor cell proliferation. We concluded that YegW is a single-target transcription factor that senses ADPG and represses glycogen accumulation in response to the amount of glucose available to the cell. We propose renaming YegW to GgaR (repressor of glycogen accumulation).

Clinical outcomes of endoscopic submucosal dissection for esophageal squamous cell carcinoma with esophageal varices: Multicenter retrospective study.

OBJECTIVES: Clinical outcomes of endoscopic submucosal dissection (ESD) for esophageal squamous cell carcinoma (ESCC) with esophageal varices (EVs) are obscure. We aimed to elucidate the clinical outcomes of ESD for ESCC with EVs in a multicenter, retrospective study. METHODS: We established a retrospective cohort of 30 patients with ESCC complicating EVs, who underwent ESD at 11 Japanese institutions. Rates of en bloc resection and R0 resection, procedure time, and adverse events were evaluated as indicators of the feasibility and safety of ESD. Additional treatment, recurrence, and metastasis of the lesions were evaluated as indicators of the long-term efficacy of ESD. RESULTS: Portal hypertension was caused by cirrhosis, of which alcohol was the most common cause. En bloc resection was achieved in 93.3% and R0 resection in 80.0% of the patients. The median procedure time was 92 min. Adverse events included a case of uncontrolled intraoperative bleeding leading to discontinuation of ESD and a case of esophageal stricture due to extensive resection. During the follow-up period of a median for 42 months, a patient with local recurrence and another patient with liver metastasis were observed. One patient died of liver failure after receiving chemoradiotherapy as an additional treatment after ESD. No patient died of ESCC. CONCLUSION: This multicenter, retrospective cohort study demonstrated the safety and efficacy of ESD for ESCC with EVs. Further studies are needed to establish appropriate treatment methods for EVs before ESD and additional treatments for patients with insufficient ESD.

Cell-growth phase-dependent promoter replacement approach for improved poly(lactate-co-3-hydroxybutyrate) production in Escherichia coli.

Escherichia coli is a useful platform for producing valuable materials through the implementation of synthetic gene(s) derived from other organisms. The production of lactate (LA)-based polyester poly[LA-co-3-hydroxybutyrate (3HB)] was carried out in E. coli using a set of five other species-derived genes: Pseudomonas sp. 61-3-derived phaC1STQK (for polymerization), Cupriavidus necator-derived phaAB (for 3HB-CoA generation), and Megasphaera elsdenii-derived pct (for LA-CoA generation) cloned into pTV118NpctphaC1ps(ST/QK)AB. Here, we aimed to optimize the expression level and timing of these genes to improve the production of P(LA-co-3HB) and to manipulate the LA fraction by replacing the promoters with various promoters in E. coli. Evaluation of the effects of 21 promoter replacement plasmids revealed that the phaC1STQK-AB operon is critical for the stationary phase for P(LA-co-3HB) production. Interestingly, the effects of the promoters depended on the composition of the medium. In glucose-supplemented LB medium, the dps promoter replacement plasmid resulted in the greatest effect, increasing the accumulation to 8.8 g/L and an LA fraction of 14.1 mol% of P(LA-co-3HB), compared to 2.7 g/L and 8.1 mol% with the original plasmid. In xylose-supplemented LB medium, the yliH promoter replacement plasmid resulted in the greatest effect, with production of 5.6 g/L and an LA fraction of 40.2 mol% compared to 3.6 g/L and 22.6 mol% with the original plasmid. These results suggest that the selection of an appropriate promoter for expression of the phaC1STQK-AB operon could improve the production and LA fraction of P(LA-co-3HB). Here, we propose that the selection of cell-growth phase-dependent promoters is a versatile biotechnological strategy for effective intracellular production of polymeric materials such as P(LA-co-3HB), in combination with the selection of sugar-based carbon sources.

Expanded roles of lactate-sensing LldR in transcription regulation of the Escherichia coli K-12 genome: lactate utilisation and acid resistance.

LldR is a lactate-responsive transcription factor (TF) that transcriptionally regulates the lldPRD operon consisting of lactate permease and lactate dehydrogenase. The lldPRD operon facilitates the utilisation of lactic acid in bacteria. However, the role of LldR in whole genomic transcriptional regulation, and the mechanism involved in adaptation to lactate remains unclear. We used genomic SELEX (gSELEX) to comprehensively analyse the genomic regulatory network of LldR to understand the overall regulatory mechanism of lactic acid adaptation of the model intestinal bacterium Escherichia coli. In addition to the involvement of the lldPRD operon in utilising lactate as a carbon source, genes related to glutamate-dependent acid resistance and altering the composition of membrane lipids were identified as novel targets of LldR. A series of in vitro and in vivo regulatory analyses led to the identification of LldR as an activator of these genes. Furthermore, the results of lactic acid tolerance tests and co-culture experiments with lactic acid bacteria suggested that LldR plays a significant role in adapting to the acid stress induced by lactic acid. Therefore, we propose that LldR is an l-/d-lactate sensing TF for utilising lactate as a carbon source and for resistance to lactate-induced acid stress in intestinal bacteria.

Overview of the Molecular Mechanism of Bacterial Environmental Adaptation by Comprehensive Analysis.

So far, the genome sequences of more than tens of thousands of organisms have been determined, and the overall picture of the genes that make up one organism has been clarified [https://www [...].

Metal-Responsive Transcription Factors Co-Regulate Anti-Sigma Factor (Rsd) and Ribosome Dimerization Factor Expression.

Bacteria exposed to stress survive by regulating the expression of several genes at the transcriptional and translational levels. For instance, in Escherichia coli, when growth is arrested in response to stress, such as nutrient starvation, the anti-sigma factor Rsd is expressed to inactivate the global regulator RpoD and activate the sigma factor RpoS. However, ribosome modulation factor (RMF) expressed in response to growth arrest binds to 70S ribosomes to form inactive 100S ribosomes and inhibit translational activity. Moreover, stress due to fluctuations in the concentration of metal ions essential for various intracellular pathways is regulated by a homeostatic mechanism involving metal-responsive transcription factors (TFs). Therefore, in this study, we examined the binding of a few metal-responsive TFs to the promoter regions of rsd and rmf through promoter-specific TF screening and studied the effects of these TFs on the expression of rsd and rmf in each TF gene-deficient E. coli strain through quantitative PCR, Western blot imaging, and 100S ribosome formation analysis. Our results suggest that several metal-responsive TFs (CueR, Fur, KdpE, MntR, NhaR, PhoP, ZntR, and ZraR) and metal ions (Cu2+, Fe2+, K+, Mn2+, Na+, Mg2+, and Zn2+) influence rsd and rmf gene expression while regulating transcriptional and translational activities.

Genomic SELEX Reveals Pervasive Role of the Flagella Master Regulator FlhDC in Carbon Metabolism.

Flagella are vital bacterial organs that allow microorganisms to move to favorable environments. However, their construction and operation consume a large amount of energy. The master regulator FlhDC mediates all flagellum-forming genes in E. coli through a transcriptional regulatory cascade, the details of which remain elusive. In this study, we attempted to uncover a direct set of target genes in vitro using gSELEX-chip screening to re-examine the role of FlhDC in the entire E. coli genome regulatory network. We identified novel target genes involved in the sugar utilization phosphotransferase system, sugar catabolic pathway of glycolysis, and other carbon source metabolic pathways in addition to the known flagella formation target genes. Examining FlhDC transcriptional regulation in vitro and in vivo and its effects on sugar consumption and cell growth suggested that FlhDC activates these new targets. Based on these results, we proposed that the flagella master transcriptional regulator FlhDC acts in the activation of a set of flagella-forming genes, sugar utilization, and carbon source catabolic pathways to provide coordinated regulation between flagella formation, operation and energy production.

Treatment strategy after noncurative endoscopic resection for early gastric cancers in patients aged ≥ 85 years: a multicenter retrospective study in a highly aged area of Japan.

BACKGROUND: The guidelines recommend additional gastrectomy after noncurative endoscopic resection for early gastric cancers (EGCs). However, no additional treatment might be acceptable in some patients aged ≥ 85 years. We aimed to identify this patient group using the data in a highly aged area. METHODS: We enrolled patients aged ≥ 85 years after noncurative endoscopic resection for EGCs at 30 institutions of the Tohoku district in Japan between 2002 and 2017. Treatment selection and prognosis after noncurative endoscopic resection were investigated. Fourteen candidates were evaluated using the Cox model to identify risk factors for poor overall survival (OS) in patients with no additional treatment. RESULTS: Of 1065 patients aged ≥ 85 years, 143 underwent noncurative endoscopic resection. Despite the guidelines' recommendation, 88.8% of them underwent no additional treatment. The 5-year OS rates in those with additional gastrectomy and those with no additional treatment were 63.1 and 65.2%, respectively. Multivariate analysis showed independent risk factors for poor OS in patients with no additional treatment were the high-risk category in the eCura system (hazard ratio [HR], 2.91), Charlson comorbidity index (CCI) ≥ 3 (HR, 2.78), and male (HR, 2.04). In patients with no additional treatment, nongastric cancer-specific survival was low (69.0% in 5 years), whereas disease-specific survival rates were very high in the low- and intermediate-risk categories of the eCura system (100.0 and 97.1%, respectively, in 5 years). CONCLUSIONS: No additional treatment may be acceptable in the low- and intermediate-risk categories of the eCura system in patients aged ≥ 85 years with noncurative endoscopic resection for EGCs.

Prediction model of 3-year survival after endoscopic submucosal dissection for early gastric cancer in elderly patients aged ≥ 85 years: EGC-2 model.

PURPOSE: Little is known about the prognostic factors for survival after endoscopic submucosal dissection (ESD) in elderly patients with early gastric cancer (EGC). The aim of this study is to determine prognostic factors and a prediction model of 3-year survival after ESD for EGC in patients aged ≥ 85 years. METHODS: We retrospectively evaluated the clinical outcomes of 740 patients with EGC aged ≥ 85 years, who were treated by ESD at 30 institutions in Japan. Overall survival (OS) and disease-specific survival (DSS) were calculated with the Kaplan-Meier method. Prediction models for 3-year OS after ESD were estimated using the Cox proportional hazards model based on Uno's C-statistics. RESULTS: During the follow-up period, 309 patients died of any cause and 10 patients died of gastric cancer. OS and DSS after 3 years were 82.7% and 99.2%, respectively. No significant differences in OS were found among curability categories. The Cox proportional hazards model revealed the geriatric nutritional risk index (GNRI) and the Charlson comorbidity index (CCI) to be predictors of 3-year survival. We established a final model (EGC-2 model) expressed by GNRI - (2.2×CCI) with a cutoff value of 96. The overall survival rate was significantly lower in the model value < 96 group than in the model value ≥ 96 group (P < 0.001). CONCLUSIONS: The prediction model using GNRI and CCI will be useful to support decision-making for the treatment of EGC in elderly patients aged ≥ 85 years.

Prognostic Benefit of Additional Treatment After Endoscopic Submucosal Dissection for Esophageal Squamous Cell Carcinoma.

BACKGROUND: Although additional treatment is considered for patients with esophageal squamous cell carcinoma (ESCC) invading into the muscularis mucosa (pT1a-MM) or submucosa (pT1b-SM) after endoscopic submucosal dissection (ESD), the actual benefits of this method remain to be elucidated. AIMS: We aimed to evaluate the prognostic benefits of additional treatment in such patients. METHODS: Between 2006 and 2017, we enrolled patients with pT1a-MM/pT1b-SM ESCC after ESD at 21 institutions in Japan. Overall survival (OS) and disease-specific survival (DSS) were compared between the additional treatment and follow-up groups after propensity score matching, to reduce the bias of baseline characteristics. A subgroup analysis was performed according to the pathological findings: category A, pT1a-MM but negative for lymphovascular invasion (LVI) and vertical margin (VM); category B, tumor invasion into the submucosa ≤ 200 µm but negative for LVI and VM; category C, others. RESULTS: Of 593 patients with pT1a-MM/pT1b-SM ESCC after ESD, 101 matched pairs were extracted after propensity score matching. The OSs were similar between the additional treatment and follow-up groups (80.6% vs. 78.6% in 5 years; P = 0.972). In a subgroup analysis, the OS in the additional treatment group was significantly lower than that in the follow-up group (65.7% vs. 95.2% in 5 years; P = 0.037) in category A, whereas OS did not significantly differ in category C (76.8% vs. 69.5% in 5 years; P = 0.360). CONCLUSIONS: Additional treatment after ESD in patients with pT1a-MM/pT1b-SM ESCC was not associated with an improved prognosis.

Transcription Factor SrsR (YgfI) Is a Novel Regulator for the Stress-Response Genes in Stationary Phase in Escherichia coli K-12.

Understanding the functional information of all genes and the biological mechanism based on the comprehensive genome regulation mechanism is an important task in life science. YgfI is an uncharacterized LysR family transcription factor in Escherichia coli. To identify the function of YgfI, the genomic SELEX (gSELEX) screening was performed for YgfI regulation targets on the E. coli genome. In addition, regulatory and phenotypic analyses were performed. A total of 10 loci on the E. coli genome were identified as the regulatory targets of YgfI with the YgfI binding activity. These predicted YgfI target genes were involved in biofilm formation, hydrogen peroxide resistance, and antibiotic resistance, many of which were expressed in the stationary phase. The TCAGATTTTGC sequence was identified as an YgfI box in in vitro gel shift assay and DNase-I footprinting assays. RT-qPCR analysis in vivo revealed that the expression of YgfI increased in the stationary phase. Physiological analyses suggested the participation of YgfI in biofilm formation and an increase in the tolerability against hydrogen peroxide. In summary, we propose to rename ygfI as srsR (a stress-response regulator in stationary phase).

Combined assessment of clinical and pathological prognostic factors for deciding treatment strategies for esophageal squamous cell carcinoma invading into the muscularis mucosa or submucosa after endoscopic submucosal dissection.

OBJECTIVES: We aimed to clarify the prognostic factors for patients with esophageal squamous cell carcinoma (ESCC) invading into the muscularis mucosa (pT1a-MM) or submucosa (pT1b-SM) after endoscopic submucosal dissection (ESD). METHODS: This retrospective study enrolled such patients at 21 institutions in Japan between 2006 and 2017. We evaluated 15 factors, including pathological risk categories for ESCC-specific mortality, six non-cancer-related indices, and treatment strategies. RESULTS: In the analysis of 593 patients, the 5-year overall and disease-specific survival rates were 83.0% and 97.6%, respectively. In a multivariate Cox analysis, male sex (hazard ratio [HR] 3.56), Charlson comorbidity index (CCI) ≥3 (HR 2.53), ages of 75-79 (HR 1.61) and ≥80 years (HR 2.04), prognostic nutrition index (PNI) <45 (HR 1.69), and pathological intermediate-risk (HR 1.63) and high-risk (HR 1.89) were prognostic factors. Subsequently, we developed a clinical risk classification for non-ESCC-related mortality based on the number of prognostic factors (age ≥75 years, male sex, CCI ≥3, PNI <45): low-risk, 0; intermediate-risk, 1-2; and high-risk, 3-4. The 5-year non-ESCC-related mortality rates for patients without additional treatment were 0.0%, 10.2%, and 45.8% in the low-, intermediate-, and high-risk groups, respectively. Meanwhile, the 5-year ESCC-specific mortality rates for the pathological low-, intermediate-, and high-risk groups were 0.3%, 5.3%, and 18.2%, respectively. CONCLUSIONS: We clarified prognostic factors for patients with pT1a-MM/pT1b-SM ESCC after ESD. The combined assessment of non-ESCC- and ESCC-related mortalities by the two risk classifications might help clinicians in deciding treatment strategies for such patients.

Regulatory role of CsuR (YiaU) in determination of cell surface properties of Escherichia coli K-12.

Genomic SELEX screening was performed to identify the binding sites of YiaU, an uncharacterized LysR family transcription factor, on the Escherichia coli K-12 genome. Five high-affinity binding targets of YiaU were identified, all of which were involved in the structures of the bacterial cell surface such as outer and inner membrane proteins, and lipopolysaccharides. Detailed in vitro and in vivo analyses suggest that YiaU activates these target genes. To gain insight into the effects of YiaU in vivo on physiological properties, we used phenotype microarrays, biofilm screening assays and the sensitivity against serum complement analysed using a yiaU deletion mutant or YiaU expression strain. Together, these results suggest that the YiaU regulon confers resistance to some antibiotics, and increases biofilm formation and complement sensitivity. We propose renaming YiaU as CsuR (regulator of cell surface).

Whole set of constitutive promoters for RpoN sigma factor and the regulatory role of its enhancer protein NtrC in Escherichia coli K-12.

The promoter selectivity of Escherichia coli RNA polymerase (RNAP) is determined by its promoter-recognition sigma subunit. The model prokaryote E. coli K-12 contains seven species of the sigma subunit, each recognizing a specific set of promoters. Using genomic SELEX (gSELEX) screening in vitro, we identified the whole set of 'constitutive' promoters recognized by the reconstituted RNAP holoenzyme alone, containing RpoD (σ70), RpoS (σ38), RpoH (σ32), RpoF (σ28) or RpoE (σ24), in the absence of other supporting regulatory factors. In contrast, RpoN sigma (σ54), involved in expression of nitrogen-related genes and also other cellular functions, requires an enhancer (or activator) protein, such as NtrC, for transcription initiation. In this study, a series of gSELEX screenings were performed to search for promoters recognized by the RpoN RNAP holoenzyme in the presence and absence of the major nitrogen response enhancer NtrC, the best-characterized enhancer. Based on the RpoN holoenzyme-binding sites, a total of 44 to 61 putative promoters were identified, which were recognized by the RpoN holoenzyme alone. In the presence of the enhancer NtrC, the recognition target increased to 61-81 promoters. Consensus sequences of promoters recognized by RpoN holoenzyme in the absence and presence of NtrC were determined. The promoter activity of a set of NtrC-dependent and -independent RpoN promoters was verified in vivo under nitrogen starvation, in the presence and absence of RpoN and/or NtrC. The promoter activity of some RpoN-recognized promoters increased in the absence of RpoN or NtrC, supporting the concept that the promoter-bound NtrC-enhanced RpoN holoenzyme functions as a repressor against RpoD holoenzyme. Based on our findings, we propose a model in which the RpoN holoenzyme fulfils the dual role of repressor and transcriptase for the same set of genes. We also propose that the promoter recognized by RpoN holoenzyme in the absence of enhancers is the 'repressive' promoter. The presence of high-level RpoN sigma in growing E. coli K-12 in rich medium may be related to the repression role of a set of genes needed for the utilization of ammonia as a nitrogen source in poor media. The list of newly identified regulatory targets of RpoN provides insight into E. coli survival under nitrogen-depleted conditions in nature.

Single-Target Regulators Constitute the Minority Group of Transcription Factors in Escherichia coli K-12.

The identification of regulatory targets of all transcription factors (TFs) is critical for understanding the entire network of genome regulation. A total of approximately 300 TFs exist in the model prokaryote Escherichia coli K-12, but the identification of whole sets of their direct targets is impossible with use of in vivo approaches. For this end, the most direct and quick approach is to identify the TF-binding sites in vitro on the genome. We then developed and utilized the gSELEX screening system in vitro for identification of more than 150 E. coli TF-binding sites along the E. coli genome. Based on the number of predicted regulatory targets, we classified E. coli K-12 TFs into four groups, altogether forming a hierarchy ranging from a single-target TF (ST-TF) to local TFs, global TFs, and nucleoid-associated TFs controlling as many as 1,000 targets. Using the collection of purified TFs and a library of genome DNA segments from a single and the same E. coli K-12, we identified here a total of 11 novel ST-TFs, CsqR, CusR, HprR, NorR, PepA, PutA, QseA, RspR, UvrY, ZraR, and YqhC. The regulation of single-target promoters was analyzed in details for the hitherto uncharacterized QseA and RspR. In most cases, the ST-TF gene and its regulatory target genes are adjacently located on the E. coli K-12 genome, implying their simultaneous transfer in the course of genome evolution. The newly identified 11 ST-TFs and the total of 13 hitherto identified altogether constitute the minority group of TFs in E. coli K-12.

Hierarchy of transcription factor network in Escherichia coli K-12: H-NS-mediated silencing and Anti-silencing by global regulators.

Transcriptional regulation for genome expression determines growth and adaptation of single-cell bacteria that are directly exposed to environment. The transcriptional apparatus in Escherichia coli K-12 is composed of RNA polymerase core enzyme and two groups of its regulatory proteins, seven species of promoter-recognition subunit sigma and about 300 species of transcription factors. The identification of regulatory targets for all these regulatory proteins is critical toward understanding the genome regulation as a whole. For this purpose, we performed a systematic search in vitro of the whole set of binding sites for each factor by gSELEX system. This review summarizes the accumulated knowledge of regulatory targets for more than 150 TFs from E. coli K-12. Overall TFs could be classified into four families: nucleoid-associated bifunctional TFs; global regulators; local regulators; and single-target regulators, in which the regulatory functions remain uncharacterized for the nucleoid-associated TFs. Here we overview the regulatory targets of two nucleoid-associated TFs, H-NS and its paralog StpA, both together playing the silencing role of a set of non-essential genes. Participation of LeuO and other global regulators have been indicated for the anti-silencing. Finally, we propose the hierarchy of TF network as a key framework of the bacterial genome regulation.

Acetate overflow metabolism regulates a major metabolic shift after glucose depletion in Escherichia coli.

Acetate overflow refers to the metabolism by which a large part of carbon incorporated as glucose into Escherichia coli cells is catabolized and excreted as acetate into the medium. We previously found that mutants for the acetate overflow pathway enzymes phosphoacetyltransferase (Pta) and acetate kinase (AckA) showed significant diauxic growth after glucose depletion in E. coli. Here, we analyzed the underlying mechanism in the pta mutant. Proteomic and other analyses revealed an increase in pyruvate dehydrogenase complex subunits and a decrease in glyoxylate shunt enzymes, which resulted from pyruvate accumulation. Since restoration of these enzyme levels by overexpressing PdhR (pyruvate-sensing transcription factor) or deleting iclR (gene encoding a pyruvate- and glyoxylate-sensing transcription factor) alleviated the growth lag of the pta mutant after glucose depletion, these changes were considered as the reason for the phenotype. Given the evidence for decreased coenzyme A (HS-CoA) levels in the pta mutant, the growth inhibition after glucose depletion was partly explained by limited availability of HS-CoA in the cell. The findings provide insights into the role of acetate overflow in metabolic regulation, which may be useful for biotechnological applications.

Molecular Basis of Sulfosugar Selectivity in Sulfoglycolysis.

The sulfosugar sulfoquinovose (SQ) is produced by essentially all photosynthetic organisms on Earth and is metabolized by bacteria through the process of sulfoglycolysis. The sulfoglycolytic Embden-Meyerhof-Parnas pathway metabolizes SQ to produce dihydroxyacetone phosphate and sulfolactaldehyde and is analogous to the classical Embden-Meyerhof-Parnas glycolysis pathway for the metabolism of glucose-6-phosphate, though the former only provides one C3 fragment to central metabolism, with excretion of the other C3 fragment as dihydroxypropanesulfonate. Here, we report a comprehensive structural and biochemical analysis of the three core steps of sulfoglycolysis catalyzed by SQ isomerase, sulfofructose (SF) kinase, and sulfofructose-1-phosphate (SFP) aldolase. Our data show that despite the superficial similarity of this pathway to glycolysis, the sulfoglycolytic enzymes are specific for SQ metabolites and are not catalytically active on related metabolites from glycolytic pathways. This observation is rationalized by three-dimensional structures of each enzyme, which reveal the presence of conserved sulfonate binding pockets. We show that SQ isomerase acts preferentially on the ß-anomer of SQ and reversibly produces both SF and sulforhamnose (SR), a previously unknown sugar that acts as a derepressor for the transcriptional repressor CsqR that regulates SQ-utilization. We also demonstrate that SF kinase is a key regulatory enzyme for the pathway that experiences complex modulation by the metabolites SQ, SLA, AMP, ADP, ATP, F6P, FBP, PEP, DHAP, and citrate, and we show that SFP aldolase reversibly synthesizes SFP. This body of work provides fresh insights into the mechanism, specificity, and regulation of sulfoglycolysis and has important implications for understanding how this biochemistry interfaces with central metabolism in prokaryotes to process this major repository of biogeochemical sulfur.