A conserved helix-unfolding motif in the naturally unfolded proteins.

Among the naturally unfolded proteins there are many polypeptides that retain an extended conformation in the absence of any apparent signal. Using sequence alignment and secondary structure prediction tools, a conserved (LS/SL)(D/E)(D/E)(D/E)X(E/D) motif is uncovered in the vicinity of the N-terminus of their unfolded helices. A comparison of these data with published observations allows one to propose that the (LS/SL)(D/E)(D/E)(D/E)X(E/D) motif is a helix-unfolding signal. Furthermore, the strong similarity between this motif and the STXXDE casein kinase II phosphorylation site suggests a regulatory mechanism for the naturally unfolded proteins within the cell.

[Neumopericardium and spontaneous post partum subcutaneus emphysema. A case report and literature review]. / Neumopericardio y enfisema subcutáneo espontáneos posparto. Presentación de un caso y revision de la literatura.

The barotrauma cases related to childbirth are an uncommon event, especially the neumopericardium. This entity must be suspected in a patient with subcutaneuos emphysema and confirmed by chest X-ray. The management is based on closed observation, support measures and antibiotic to prevent infection. The radiological follow up is important to evaluate the resolution of this problem. The patient must be followed with caution if the neumopericardium increases because this could lead to a cardiac tamponade with fatal consequences. The description of a case diagnosed and managed in our hospital is done herein which evolution was satisfactory towards resolution of the pneumopericardium without the need of further intervention.

Caspase-1-inhibitor ac-YVAD-cmk reduces LPS-lethality in rats without affecting haematology or cytokine responses.

The effect of acetyl - tyrosyl-valyl-alanyl-aspartyl - chloromethylketone (ac-YVAD-cmk), an irreversible caspase-1 (IL-1beta converting enzyme, ICE) inhibitor on mortality, leukocyte and platelet counts and cytokine levels was investigated in a double-blind rat model of endotoxaemia. Intravenous (i.v.) bolus administration of lipopolysaccharide (LPS) (25-75 mg kg(-1), n=12 per group) to anaesthetized rats induced a dose dependent increase in mortality over 8 h (LD(50)=48 mg kg(-1)). During this period, animals became leukopenic and thrombocytopenic. Serum levels of IL-beta, IL-6, and TNF-alpha were highly elevated. Pretreatment of rats with ac-YVAD-cmk at a dose of 12.5 micromol kg(-1) significantly reduced mortality from 83 to 33% using Log Rank analysis. However, ac-YVAD-cmk did not modify blood cell counts or cytokine profiles as compared with the LPS-drug vehicle group. These data lay credence to the potential importance of caspase-1-inhibition in modifying the inflammatory response to endotoxin. Further investigations are warranted in understanding the relationship between caspase-1 inhibition, cytokine production and animal survival in different experimental paradigms of sepsis.

Characterization of the calcium and chloride [3H]glutamate binding site in crude synaptic membranes from human brain tissue.

1. The specific binding properties of [3H]glutamate to crude synaptic membranes (CSM) from postmortem human brain were studied. 2. Equilibrium binding analysis of [3H]glutamate binding to CSM from human brain cortex revealed a KD = 110 +/- 12 nM and a Bmax = 27 +/- 4 pmol/mg protein). 3. Calcium increased the number of binding sites, Bmax = 44 +/- 6 pmol/mg protein, without a significant change in the affinity constant, KD = 95 +/- 10 nM. 4. The dissociation constant of the [3H]glutamate bound to human CSM was 4.0 +/- 0.4 min-1 (n = 3). 5. The relative potencies of glutamate analogs and 2-amino-4-phosphonobutyric acid (APB) to compete for the glutamate binding sites, in human CSM, were glutamate > quisqualate = ibotenic acid > APB >> alpha-amino-3-hydroxy-5-methyl-4-isoxozolepropionate acid. 6. The glutamate specific binding in CSM from postmortem human brain was particularly rich in the gyrus hippocampus, nucleus accumbens, thalamus and frontal cortex. 7. This glutamate binding protein is related, probably, to a presynaptic neurosecretory pathway.

Molecular structure and early events in the replication of Tacaribe arenavirus S RNA.

Tacaribe arenavirus S RNA was cloned and analysis of its nucleotide sequence revealed two open reading frames of significant size, one in the virus-sense strand, the other in the virus-complementary strand. The predicted amino acid sequences of the two reading frames were compared with the predicted primary structures of the nucleoprotein (N) and glycoprotein precursor (GPC) of LCM, Pichinde and Lassa viruses. The results indicated a high degree of homology between the proteins of similar properties. It was also found that in Tacaribe virus-infected cells a subgenomic viral-sense GPC RNA and a subgenomic viral-complementary N RNA are synthesized in addition to the full length viral (v) RNA and viral complementary (vc) RNAs. These results support the conclusion that in Tacaribe virus--as in Pichinde and lymphocytic choriomeningitis arenavirus-S RNA encodes the viral N and GPC proteins and has an 'ambisense' coding strategy. Analysis of the S-derived RNA species at early times post-infection in cells incubated with or without inhibitors of protein synthesis indicated that for primary transcription of the N mRNA, protein synthesis is not required; whereas synthesis of the vc RNA, GPC mRNA and v RNA does require protein synthesis to take place.

A comparative study of the thermal inactivation of the isolated and associated domains within the beta 2 subunit of Escherichia coli tryptophan synthetase. Evidence for strong interdomain interactions.

The irreversible inactivation by heat of the F1 and F2 regions of the beta 2 subunit of Escherichia coli tryptophan synthetase (L-serine hydrolyase (adding indole) EC 4.2.1.20) has been studied. By comparing the kinetics of inactivation of the F1 and F2 fragments, either isolated by proteolysis or associated within the beta 2 protein, it is shown that the F1 fragment is protected considerably against heat inactivation by its interactions with the complementary F2 fragment. An important stabilization of the protein conformation by the coenzyme, pyridoxal 5'-phosphate, is also observed. By using a hybrid enzyme preparation, it is shown that the stabilization by a single pyridoxal 5'-phosphate molecule of the two protomers within beta 2 is likely to be caused by a strengthening of interdomain interactions upon binding of the coenzyme. These results point to a strong energetic coupling between the two domains of the beta chain.