Role of Synonymous Mutations in the Evolution of TEM ß-Lactamase Genes.

Nonsynonymous mutations are well documented in TEM ß-lactamases. The resulting amino acid changes often alter the conferred phenotype from broad spectrum (2b) conferred by TEM-1 to extended spectrum (2be), inhibitor resistant (2br), or both extended spectrum and inhibitor resistant (2ber). The encoding blaTEM genes also deviate in numerous synonymous mutations, which are not well understood. blaTEM-3 (2be), blaTEM-33 (2br), and blaTEM-109 (2ber) were studied in comparison to blaTEM-1blaTEM-33 was chosen for more detailed studies because it deviates from blaTEM-1 by a single nonsynonymous mutation and three additional synonymous mutations. Genes encoding the enzymes with only nonsynonymous or all (including synonymous) mutations plus all permutations between blaTEM-1 and blaTEM-33 were expressed in Escherichia coli cells. In disc diffusion assays, genes encoding TEM-3, TEM-33, and TEM-109 with all synonymous mutations resulted in higher resistance levels than genes without synonymous mutations. Disc diffusion assays with the 16 genes carrying all possible nucleotide change combinations between blaTEM-1 and blaTEM-33 indicated different susceptibilities for different variants. Nucleotide BLAST searches did not identify genes without synonymous mutations but did identify some without nonsynonymous mutations. Energies of possible secondary mRNA structures calculated with mfold are generally higher with synonymous mutations, suggesting that their role could be to destabilize the mRNA and facilitate its unfolding for efficient translation. In summary, our data indicate that transition from blaTEM-1 to other variant genes by simply acquiring the nonsynonymous mutations is not favored. Instead, synonymous mutations seem to support the transition to other variant genes with nonsynonymous mutations leading to different phenotypes.

The Bacteroidetes Aequorivita sp. and Kaistella jeonii Produce Promiscuous Esterases With PET-Hydrolyzing Activity.

Certain members of the Actinobacteria and Proteobacteria are known to degrade polyethylene terephthalate (PET). Here, we describe the first functional PET-active enzymes from the Bacteroidetes phylum. Using a PETase-specific Hidden-Markov-Model- (HMM-) based search algorithm, we identified several PETase candidates from Flavobacteriaceae and Porphyromonadaceae. Among them, two promiscuous and cold-active esterases derived from Aequorivita sp. (PET27) and Kaistella jeonii (PET30) showed depolymerizing activity on polycaprolactone (PCL), amorphous PET foil and on the polyester polyurethane Impranil® DLN. PET27 is a 37.8 kDa enzyme that released an average of 174.4 nmol terephthalic acid (TPA) after 120 h at 30°C from a 7 mg PET foil platelet in a 200 µl reaction volume, 38-times more than PET30 (37.4 kDa) released under the same conditions. The crystal structure of PET30 without its C-terminal Por-domain (PET30ΔPorC) was solved at 2.1 Å and displays high structural similarity to the IsPETase. PET30 shows a Phe-Met-Tyr substrate binding motif, which seems to be a unique feature, as IsPETase, LCC and PET2 all contain Tyr-Met-Trp binding residues, while PET27 possesses a Phe-Met-Trp motif that is identical to Cut190. Microscopic analyses showed that K. jeonii cells are indeed able to bind on and colonize PET surfaces after a few days of incubation. Homologs of PET27 and PET30 were detected in metagenomes, predominantly aquatic habitats, encompassing a wide range of different global climate zones and suggesting a hitherto unknown influence of this bacterial phylum on man-made polymer degradation.

Simulation Foundry: Automated and F.A.I.R. Molecular Modeling.

The Simulation Foundry (SF) is a modular workflow for the automated creation of molecular modeling (MM) data. MM allows for the reliable prediction of the microscopic and macroscopic properties of multicomponent systems from first principles. The SF makes MM repeatable, replicable, and findable, accessible, interoperable, and reusable (F.A.I.R.). The SF uses a standardized data structure and file naming convention, allowing for replication on different supercomputers and re-entrancy. We focus on keeping the SF simple by basing it on scripting languages that are widely used by the MM community (bash, Python) and making it reusable and re-editable. The SF was developed to assist expert users in performing parameter studies of multicomponent systems by high throughput molecular dynamics simulations. The usability of the SF is demonstrated by simulations of thermophysical properties of binary mixtures. A standardized data exchange format enables the integration of simulated data with data from experiments. The SF also provides a complete documentation of how the results were obtained, thus assigning provenance. Increasing computational power facilitates the intensification of the simulation process and requires automation and modularity. The SF provides a community platform on which to integrate new methods and create data that is reproducible and transparent (https://fairdomhub.org/studies/639/snapshots/1, https://fairdomhub.org/studies/639/snapshots/2).

Diverse effects of aqueous polar co-solvents on Candida antarctica lipase B.

Biocatalysis in mixtures of water and co-solvents represents an opportunity to expand the application of enzymes. However, in the presence of organic solvents, enzymes can undergo reversible inhibition, inactivation, or aggregation. In this work, we studied the effects of three co-solvents (methanol, acetone, and dimethyl sulfoxide - DMSO) on the function and structure of the recombinant Candida antarctica lipase B (rCALB), a widely used enzyme in biotechnological applications. The effects of co-solvents on rCALB were investigated by steady-state kinetics experiments, biophysical assays and by molecular dynamics simulations in the presence and upon incubation with the three co-solvents. Methanol and acetone were found to act as competitive inhibitors of rCALB and to promote its aggregation, whereas DMSO is a non-essential activator of rCALB.

Structural basis of steroid binding and oxidation by the cytochrome P450 CYP109E1 from Bacillus megaterium.

Cytochrome P450 monooxygenases (P450s) are attractive enzymes for the pharmaceutical industry, in particular, for applications in steroidal drug synthesis. Here, we report a comprehensive functional and structural characterization of CYP109E1, a novel steroid-converting cytochrome P450 enzyme identified from the genome of Bacillus megaterium DSM319. In vitro and whole-cell in vivo turnover experiments, combined with binding assays, revealed that CYP109E1 is able to hydroxylate testosterone at position 16ß. Related steroids with bulky substituents at carbon C17, like corticosterone, bind to the enzyme without being converted. High-resolution X-ray structures were solved of a steroid-free form of CYP109E1 and of complexes with testosterone and corticosterone. The structural analysis revealed a highly dynamic active site at the distal side of the heme, which is wide open in the absence of steroids, can bind four ordered corticosterone molecules simultaneously, and undergoes substantial narrowing upon binding of single steroid molecules. In the crystal structures, the single bound steroids adopt unproductive binding modes coordinating the heme-iron with their C3-keto oxygen. Molecular dynamics (MD) simulations suggest that the steroids may also bind in ~180° reversed orientations with the C16 carbon and C17-substituents pointing toward the heme, leading to productive binding of testosterone explaining the observed regio- and stereoselectivity. The X-ray structures and MD simulations further identify several residues with important roles in steroid binding and conversion, which could be confirmed by site-directed mutagenesis. Taken together, our results provide unique insights into the CYP109E1 activity, substrate specificity, and regio/stereoselectivity. DATABASE: The atomic coordinates and structure factors have been deposited in the Protein Data Bank with accession codes 5L90 (steroid-free CYP109E1), 5L91 (CYP109E1-COR4), 5L94 (CYP109E1-TES), and 5L92 (CYP109E1-COR). ENZYMES: Cytochrome P450 monooxygenase CYP109E1, EC 1.14.14.1, UniProt ID: D5DKI8, Adrenodoxin reductase EC 1.18.1.6.

SHV Lactamase Engineering Database: a reconciliation tool for SHV ß-lactamases in public databases.

BACKGROUND: SHV ß-lactamases confer resistance to a broad range of antibiotics by accumulating mutations. The number of SHV variants is steadily increasing. 117 SHV variants have been assigned in the SHV mutation table (http://www.lahey.org/Studies/). Besides, information about SHV ß-lactamases can be found in the rapidly growing NCBI protein database. The SHV ß-Lactamase Engineering Database (SHVED) has been developed to collect the SHV ß-lactamase sequences from the NCBI protein database and the SHV mutation table. It serves as a tool for the detection and reconciliation of inconsistencies, and for the identification of new SHV variants and amino acid substitutions. DESCRIPTION: The SHVED contains 200 protein entries with distinct sequences and 20 crystal structures. 83 protein sequences are included in the both the SHV mutation table and the NCBI protein database, while 35 and 82 protein sequences are only in the SHV mutation table and the NCBI protein database, respectively. Of these 82 sequences, 41 originate from microbial sources, and 22 of them are full-length sequences that harbour a mutation profile which has not been classified yet in the SHV mutation table. 27 protein entries from the NCBI protein database were found to have an inconsistency in SHV name identification. These inconsistencies were reconciled using information from the SHV mutation table and stored in the SHVED.The SHVED is accessible at http://www.LacED.uni-stuttgart.de/classA/SHVED/. It provides sequences, structures, and a multisequence alignment of SHV ß-lactamases with the corrected annotation. Amino acid substitutions at each position are also provided. The SHVED is updated monthly and supplies all data for download. CONCLUSIONS: The SHV ß-Lactamase Engineering Database (SHVED) contains information about SHV variants with reconciled annotation. It serves as a tool for detection of inconsistencies in the NCBI protein database, helps to identify new mutations resulting in new SHV variants, and thus supports the investigation of sequence-function relationships of SHV ß-lactamases.

Morphing activity between structurally similar enzymes: from heme-free bromoperoxidase to lipase.

In this study, to explore the plasticity of the alpha/beta-hydrolase fold family, we converted bromoperoxidase A2 (BPO-A2) from Streptomyces aureofaciens to a lipase by structure comparison with lipase A (LipA) from Bacillus subtilis. These two enzymes have similar structures (2.1 A rmsd) and a very low level of sequence identity ( approximately 18%). A variant BL1 was constructed by deleting the caplike domain of BPO-A2 and further fine-tuning the newly formed substrate binding site. The lipase activity was successfully transplanted on BL1, while the halogenation activity was totally lost. BL1 also showed higher hydrolytic activities toward long chain p-nitrophenyl esters, such as p-nitrophenyl caprylate (3.7-fold) and p-nitrophenyl palmitate (7.0-fold), while its activity toward a short chain ester (p-nitrophenyl acetate) decreased dramatically, to only 1.2% of that of BPO-A2. After two rounds of directed evolution and site-directed mutagenesis on selected residues, several mutants with both improved hydrolytic activities and substrate preferences toward long chain substrates were obtained. The highest hydrolytic activity toward p-nitrophenyl palmitate of the best mutant BL1-2-E8-plusI was improved by 40-fold compared with that of BL1. These results demonstrate the possibility of manipulating the caplike domain of alpha/beta-hydrolase fold enzymes and provide further understanding of the structure-function relationship of the alpha/beta-hydrolase fold enzymes. The design strategy used in this study could serve as a useful approach for constructing variants with targeted catalytic properties using the alpha/beta-hydrolase fold.

Cloning, expression and characterisation of CYP102A7, a self-sufficient P450 monooxygenase from Bacillus licheniformis.

Cytochrome P450 monooxygenases of the CYP102A subfamily are single-component natural fusion proteins consisting of a heme domain and a diflavin reductase. The characterised CYP102A enzymes are fatty acid hydroxylases with turnover rates of several thousands per minute. In search of new P450s with similar activities, but with a broader substrate spectrum, we cloned, expressed and characterised CYP102A7 from Bacillus licheniformis. As expected, CYP102A7 was active towards medium-chain fatty acids but showed a strong preference for saturated over unsaturated fatty acids, which could not be observed for either of the CYP102A members so far. Besides fatty acids, CYP102A7 was able to catalyse the oxidation of cyclic and acyclic terpenes with high activity and coupling efficiency. For example, (R)-(+)-limonene was converted with activity of 220 nmol nmol P450(-1) min(-1) and 80% coupling. Unusual for enzymes of the CYP102A subfamily was the deethylation activity of CYP102A7 towards 7-ethoxycoumarin. Furthermore, this monooxygenase, though having a moderate thermal stability, exhibited 50% of its initial activity in the presence of 26% DMSO. Comparison of the homology models of CYP102A7 and other members of the CYP102A subfamily revealed distinct differences in the shape of the substrate access channel and the active site, which might explain differences in catalytic properties of these homologous enzymes.

The Cytochrome P450 Engineering Database: a navigation and prediction tool for the cytochrome P450 protein family.

SUMMARY: The Cytochrome P450 Engineering Database (CYPED) has been designed to serve as a tool for a comprehensive and systematic comparison of protein sequences and structures within the vast and diverse family of cytochrome P450 monooxygenases (CYPs). The CYPED currently integrates sequence and structure data of 3911 and 25 proteins, respectively. Proteins are grouped into homologous families and superfamilies according to Nelson's classification. Nonclassified CYP sequences are assigned by similarity. Functionally relevant residues are annotated. The web accessible version contains multisequence alignments, phylogenetic trees and HMM profiles. The CYPED is regularly updated and supplies all data for download. Thus, it provides a valuable data source for phylogenetic analysis, investigation of sequence-function relationships and the design of CYPs with improved biochemical properties. ABBREVIATIONS: Cytochrome P450 Engineering Database, CYPED; cytochrome P450 monooxygenase, CYP; Hidden Markov Model, HMM. AVAILABILITY: www.cyped.uni-stuttgart.de

Hydroxyl groups in the betabeta sandwich of metallo-beta-lactamases favor enzyme activity: Tyr218 and Ser262 pull down the lid.

Metallo-beta-lactamases (MBLs) efficiently hydrolyze and thereby inactivate various beta-lactam antibiotics in clinical use. Their potential to evolve into more efficient enzymes threatens public health. Recently, we have identified the designed F218Y mutant of IMP-1 as an enzyme with superior catalytic efficiency compared to the wild-type. Thus, it may be found in clinical isolates in the future. In an effort to elucidate the molecular mechanisms involved in enhanced activity, we carried out molecular dynamics simulations of ten MBL variants in complex with a cefotaxime intermediate. The stability of these near-transition state enzyme-substrate intermediate complexes was modeled and compared to the experimental catalytic efficiencies k(cat)/K(M). For each of the ten complexes ten independent simulations were performed. In each simulation the temperature was gradually increased and determined upon breakdown of the complex. Rankings based on the experimental catalytic efficiencies and the data from computer simulations were in good agreement. From trajectory analysis of stable simulations, the combination of Tyr218 and Ser262 was found to lead to an altered hydrogen bonding network, which translates into a closing down movement of a beta-hairpin loop covering the active site. These observations may explain the significantly decreased K(M) and increased k(cat)/K(M) values of this variant toward all substrates recently tested in experiment. Previously, we have discovered that mutations G262S (yielding IMP-1) and G262A in IMP-6 stabilize the Zn(II) ligand His263 and thus the enzyme-substrate intermediate complex through a domino effect, which enhances conversion of drugs like ceftazidime, penicillins, and imipenem. Together, the domino effect and the altered beta-hairpin loop conformation explain how IMP-6 can evolve through mutations G262S and F218Y into an enzyme with up to one order of magnitude increased catalytic efficiencies toward these important antibiotics. Furthermore, the previously proposed binding of a third zinc ion close to the active site of IMP-6 mutant S121G was corroborated by our simulations.

Biochemical profiling in silico--predicting substrate specificities of large enzyme families.

A general high-throughput method for in silico biochemical profiling of enzyme families has been developed based on covalent docking of potential substrates into the binding sites of target enzymes. The method has been tested by systematically docking transition state--analogous intermediates of 12 substrates into the binding sites of 20 alpha/beta hydrolases from 15 homologous families. To evaluate the effect of side chain orientations to the docking results, 137 crystal structures were included in the analysis. A good substrate must fulfil two criteria: it must bind in a productive geometry with four hydrogen bonds between the substrate and the catalytic histidine and the oxyanion hole, and a high affinity of the enzyme-substrate complex as predicted by a high docking score. The modelling results in general reproduce experimental data on substrate specificity and stereoselectivity: the differences in substrate specificity of cholinesterases toward acetyl- and butyrylcholine, the changes of activity of lipases and esterases upon the size of the acid moieties, activity of lipases and esterases toward tertiary alcohols, and the stereopreference of lipases and esterases toward chiral secondary alcohols. Rigidity of the docking procedure was the major reason for false positive and false negative predictions, as the geometry of the complex and docking score may sensitively depend on the orientation of individual side chains. Therefore, appropriate structures have to be identified. In silico biochemical profiling provides a time efficient and cost saving protocol for virtual screening to identify the potential substrates of the members of large enzyme family from a library of molecules.

Impact of remote mutations on metallo-beta-lactamase substrate specificity: implications for the evolution of antibiotic resistance.

Metallo-beta-lactamases have raised concerns due to their ability to hydrolyze a broad spectrum of beta-lactam antibiotics. The G262S point mutation distinguishing the metallo-beta-lactamase IMP-1 from IMP-6 has no effect on the hydrolysis of the drugs cephalothin and cefotaxime, but significantly improves catalytic efficiency toward cephaloridine, ceftazidime, benzylpenicillin, ampicillin, and imipenem. This change in specificity occurs even though residue 262 is remote from the active site. We investigated the substrate specificities of five other point mutants resulting from single-nucleotide substitutions at positions near residue 262: G262A, G262V, S121G, F218Y, and F218I. The results suggest two types of substrates: type I (nitrocefin, cephalothin, and cefotaxime), which are converted equally well by IMP-6, IMP-1, and G262A, but even more efficiently by the other mutants, and type II (ceftazidime, benzylpenicillin, ampicillin, and imipenem), which are hydrolyzed much less efficiently by all the mutants. G262V, S121G, F218Y, and F218I improve conversion of type I substrates, whereas G262A and IMP-1 improve conversion of type II substrates, indicating two distinct evolutionary adaptations from IMP-6. Substrate structure may explain the catalytic efficiencies observed. Type I substrates have R2 electron donors, which may stabilize the substrate intermediate in the binding pocket. In contrast, the absence of these stabilizing interactions with type II substrates may result in poor conversion. This observation may assist future drug design. As the G262A and F218Y mutants confer effective resistance to Escherichia coli BL21(DE3) cells (high minimal inhibitory concentrations), they are likely to evolve naturally.

Structure and dynamics of Candida rugosa lipase: the role of organic solvent.

The effect of organic solvent on the structure and dynamics of proteins was investigated by multiple molecular dynamics simulations (1 ns each) of Candida rugosa lipase in water and in carbon tetrachloride. The choice of solvent had only a minor structural effect. For both solvents the open and the closed conformation of the lipase were near to their experimental X-ray structures (C(alpha) rms deviation 1-1.3 A). However, the solvents had a highly specific effect on the flexibility of solvent-exposed side chains: polar side chains were more flexible in water, but less flexible in organic solvent. In contrast, hydrophobic residues were more flexible in organic solvent, but less flexible in water. As a major effect solvent changed the dynamics of the lid, a mobile element involved in activation of the lipase, which fluctuated as a rigid body about its average position. While in water the deviations were about 1.6 A, organic solvent reduced flexibility to 0.9 A. This increase rigidity was caused by two salt bridges (Lys85-Asp284, Lys75-Asp79) and a stable hydrogen bond (Lys75-Asn 292) in organic solvent. Thus, organic solvents stabilize the lid but render the side chains in the hydrophobic substrate-binding site more mobile. [figure: see text]. Superimposition of open (black, PDB entry 1CRL) and closed (gray, PDB entry 1TRH) conformers of C. rugosa lipase. The mobile lid is indicated.

Modeling domino effects in enzymes: molecular basis of the substrate specificity of the bacterial metallo-beta-lactamases IMP-1 and IMP-6.

Metallo-beta-lactamases can hydrolyze a broad spectrum of beta-lactam antibiotics and thus confer resistance to bacteria. For the Pseudomonas aeruginosa enzyme IMP-1, several variants have been reported. IMP-6 and IMP-1 differ by a single residue (glycine and serine at position 196, respectively), but have significantly different substrate spectra; while the catalytic efficiency toward the two cephalosporins cephalothin and cefotaxime is similar for both variants, IMP-1 is up to 10-fold more efficient than IMP-6 toward cephaloridine and ceftazidime. Interestingly, this biochemical effect is caused by a residue remote from the active site. The substrate-specific impact of residue 196 was studied by molecular dynamics simulations using a cationic dummy atom approach for the zinc ions. Substrates were docked in an intermediate structure near the transition state to the binding site of IMP-1 and IMP-6. At a simulation temperature of 100 K, most complexes were stable during 1 ns of simulation time. However, at higher temperatures, some complexes became unstable and the substrate changed to a nonactive conformation. To model stability, six molecular dynamics simulations at 100 K were carried out for all enzyme-substrate complexes. Stable structures were further heated to 200 and 300 K. By counting stable structures, we derived a stability ranking score which correlated with experimentally determined catalytic efficiency. The use of a stability score as an indicator of catalytic efficiency of metalloenzymes is novel, and the study of substrates in a near-transition state intermediate structure is superior to the modeling of Michaelis complexes. The remote effect of residue 196 can be described by a domino effect: upon replacement of serine with glycine, a hole is created and a stabilizing interaction between Ser196 and Lys33 disappears, rendering the neighboring residues more flexible; this increased flexibility is then transferred to the active site.