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PJ Muchowski, MM Valdez, GJ S Wu, JI Clark; Functional Similarities Between the Small Heat Shock Proteins Mycobacterium Tuberculosis HSP 16.3 and Human aB-crystallin . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3564.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Mycobacterium tuberculosis heat shock protein 16.3 (MTB HSP16.3) accumulates as the dominant protein in the latent stationary phase of tuberculosis. MTB HSP16.3 displays several characteristics of small heat shock proteins (sHsps): its expression is increased in response to stress, it protects against protein aggregation in vitro, and it contains the core a-crystallin domain found in all sHsps. The purpose of this study was to compare the in vitro chaperone activity of MTB HSP16.3 with that of human aB-crystallin, a well-characterized member of the sHsp family. Methods: Recombinant MTB HSP16.3 was expressed in E. coli and purified to apparent homogeneity. Chaperone activity of MTB HSP16.3 was evaluated in several different assays and compared with results obtained with human aB-crystallin. Results: Similar to aB-crystallin, MTB HSP16.3 completely suppressed citrate synthase aggregation, and in the presence of 3.5 mM ATP the chaperone activity was enhanced by two-fold. ATP stabilized MTB HSP16.3 against proteolysis by chymotrypsin, and no effect was observed with ATPgS, a non-hydrolyzable analog of ATP. Increased expression of MTB HSP16.3 resulted in protection against thermal killing in E. coli at 48°C. Conclusion: While the sequence identity between human aB-crystallin and MTB HSP16.3 is only 18%, these results suggest that the functional similarities between these proteins are much closer. Our results suggest the chaperone activity of MTB HSP16.3 may play an important role in the survival and stability of latent Mycobacterium tuberculosis.
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