Open AccessFunctional similarities between the small heat shock proteins Mycobacterium tuberculosis HSP 16.3 and human αB‐crystallin
Author(s) -
Valdez Melissa M.,
Clark John I.,
Wu Gabrielle J. S.,
Muchowski Paul J.
Publication year - 2002
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1033.2002.02812.x
Subject(s) - heat shock protein , recombinant dna , mycobacterium tuberculosis , chaperone (clinical) , escherichia coli , biology , crystallin , proteolysis , microbiology and biotechnology , hspa4 , hspa14 , biochemistry , hsp70 , chemistry , enzyme , gene , tuberculosis , medicine , pathology
Mycobacterium tuberculosis heat shock protein 16.3 (MTB HSP 16.3) accumulates as the dominant protein in the latent stationary phase of tuberculosis infection. MTB HSP 16.3 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 ‘α‐crystallin’ domain found in all sHsps. In this study we characterized the chaperone activity of recombinant MTB HSP 16.3 in several different assays and compared the results to those obtained with recombinant human αB‐crystallin, a well characterized member of the sHsp family. Recombinant MTB HSP 16.3 was expressed in Escherichia coli and purified to apparent homogeneity. Similar to αB‐crystallin, MTB HSP16.3 suppressed citrate synthase aggregation and in the presence of 3.5 m m ATP the chaperone activity was enhanced by twofold. ATP stabilized MTB HSP 16.3 against proteolysis by chymotrypsin, and no effect was observed with ATPγS, a nonhydrolyzable analog of ATP. Increased expression of MTB HSP 16.3 resulted in protection against thermal killing in E. coli at 48 °C. While the sequence similarity between human αB‐crystallin and MTB HSP 16.3 is only 18%, these results suggest that the functional similarities between these proteins containing the core ‘α‐crystallin’ domain are much closer.