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Surface accessibility of the 70-kilodalton Chlamydia trachomatis heat shock protein following reduction of outer membrane protein disulfide bonds.

Abstract：

:Numerous investigations have shown that 70-kDa heat shock protein (Hsp70) homologs interact tightly with hydrophobic proteins and functionally assist proteins in membranous organelles and environments. One such protein is the Chlamydia trachomatis Hsp70 that is associated with isolated outer membrane complexes of infectious elementary bodies (EB). Previous observations have indicated that chlamydial Hsp70 plays a role in EB attachment to, or entry into, endometrial epithelial cells. In this study, immunofluorescence microscopy and transmission electron microscopy observations showed that chlamydial Hsp70 is not a surface-displayed ligand on purified EB. However, brief exposure of EB to the thiol reducing agent dithiothreitol (DTT) led to surface accessibility of the Hsp70 substrate-binding domain. Reduction of the highly disulfide-cross-linked EB outer membrane proteins with DTT resulted in a decrease in EB attachment and infectivity. Interestingly, exposure of EB to the membrane-impermeable thiol-alkylating reagent 5,5'-dithiobis(2-nitrobenzoic acid) enhanced attachment but compromised infectivity, suggesting that EB outer membrane proteins must be reduced for entry and productive infection. Together, our data suggest that (i) the structural integrity of the EB outer membrane, maintained by protein disulfide bonds, is important during the initial stages of attachment; (ii) reduction occurs within the localized microenvironment of host cell surfaces once intimate contact is established between EB and host cells; and (iii) subsequent conformational changes in EB ultrastructure allow productive infection in host cells. The accessibility of the Hsp70 substrate-binding domain may support the hypothesis that this protein plays a role in events following the initial stage of attachment instead of serving as a primary, surface-displayed adhesin.

journal_name

Infect Immun

journal_title

Infection and immunity

authors

Raulston JE,Davis CH,Paul TR,Hobbs JD,Wyrick PB

doi

10.1128/iai.70.2.535-543.2002

keywords:

subject

Has Abstract

pub_date

2002-02-01 00:00:00

pages

535-43

issue

eissn

0019-9567

issn

1098-5522

journal_volume

pub_type

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Surface accessibility of the 70-kilodalton Chlamydia trachomatis heat shock protein following reduction of outer membrane protein disulfide bonds.