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Background: Bacteria such as Escherichia coli and Salmonella typhimurium can utilize acetate as the sole source of carbon and energy. Acetate kinase (AckA) and phosphotransacetylase (Pta), key enzymes of acetate utilization pathway, regulate flux of metabolites in glycolysis, gluconeogenesis, TCA cycle, glyoxylate bypass and fatty acid metabolism. Results: Here we report kinetic characterization of S. typhimurium AckA (StAckA) and structures of its unliganded (Form-I, 2.70 Å resolution) and citrate-bound (Form-II, 1.90 Å resolution) forms. The enzyme showed broad substrate specificity with kcat/Km in the order of acetate > propionate > formate. Further, the Km for acetyl-phosphate was significantly lower than for acetate and the enzyme could catalyze the reverse reaction (i.e. ATP synthesis) more efficiently. ATP and Mg2+ could be substituted by other nucleoside 5⁄-triphosphates (GTP, UTP and CTP) and divalent cations (Mn2+ and Co2+), respectively. Form-I StAckA represents the first structural report of an unliganded AckA. StAckA protomer consists of two domains with characteristic ΒΒΒαΒαΒα topology of ASKHA superfamily of proteins. These domains adopt an intermediate conformation compared to that of open and closed forms of ligand-bound Methanosarcina thermophila AckA (MtAckA). Spectroscopic and structural analyses of StAckA further suggested occurrence of inter-domain motion upon ligand-binding. Unexpectedly, Form-II StAckA structure showed a drastic change in the conformation of residues 230-300 compared to that of Form-I. Further investigationrevealed electron density corresponding to a citrate molecule in a pocket located at the dimeric interface of Form-II StAckA. Interestingly, a similar dimeric interface pocket lined with largely conserved residues could be identified inForm-I StAckA as well as in other enzymes homologous to AckA suggesting that ligand binding at this pocket may influence the function of these enzymes.Conclusions: The biochemical and structural characterization of StAckA reported here provides insights into the biochemical specificity, overall fold, thermal stability, molecular basis of ligand binding and inter-domain motion in AckA family of enzymes. Dramatic conformational differences observed between unliganded and citrate-bound forms of StAckA led to identification of a putative ligand-binding pocket at the dimeric interface of StAckA with implications for enzymatic function. [ABSTRACT FROM AUTHOR]

Byssinosis is an occupational hazard for the workers exposed to cotton dust. In this study 616 cotton textile workers were studied; out of which 149 had byssinosis; 37 (24.7%) had grade-1/2, 78 (52.7%) grade-1, 25 (16.6%) grade-2 and 9 (6.0%) of grade-3 byssinosis. Majority of the byssinotics were of age group between 36-40 years and had developed disease after 16 years of exposure. Disease was more common among smokers and severe, in whom consumption was more than 15 cigarettes/bidis per day for more than 10 years. Ventilatory function tests were markedly abnormal compared with non-byssinotic. On clinical examination and laboratory investigation (specially eosinophilia) and, radiological investigation (x-ray chest) no positive finding was detected. The high prevalence rate of the disease in this study was apparently due to poor working conditions of the workers.