title: The association of small heat shock protein Hsp16.3 with the plasma membrane of Mycobacterium tuberculosis: dissociation of oligomers is a prerequisite.
abstract: Hsp16.3, a small heat shock protein from Mycobacterium tuberculosis (MTB), was originally identified as an immuno-dominant antigen and later found to be a major membrane protein. In vitro studies show that Hsp16.3 exists as nonamers and undergoes dynamic dissociation/re-association equilibrium in solutions. Nevertheless, neither the details nor the physiological implications of the presence of Hsp16.3 in the plasma membrane have been studied. In this study, we demonstrated that the purified Hsp16.3 proteins were able to interact with the MTB plasma membrane in a specific and reversible manner, suggesting that there might be subunit exchange between membrane-bound Hsp16.3 and soluble Hsp16.3 oligomers. The dissociation of Hsp16.3 oligomers appears to be a prerequisite for its membrane binding, which is interesting in view that the dissociation of small heat shock protein oligomers was also found to be necessary for it to bind denaturing substrate proteins. Furthermore, the oligomeric structure of Hsp16.3 seems to be more dynamic and flexible when incubating with the mycobacterium lipids. The physiological implications of these observations for Hsp16.3, and small heat shock proteins in general, are discussed.
authors.affiliation: Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.forename: Xinmiao
authors.initials: X
authors.lastname: Fu
authors.forename: Wangwang
authors.initials: W
authors.lastname: Jiao
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Zhang
authors.forename: Chong
authors.initials: C
authors.lastname: Liu
authors.forename: Zengyi
authors.initials: Z
authors.lastname: Chang
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D018833:Chaperonins / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D008563:Membrane Lipids / Q000378:metabolism; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C431133:Hsp16.3 protein, Mycobacterium tuberculosis; D008563:Membrane Lipids; D021122:Protein Subunits; D018833:Chaperonins