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The ExPortal: an organelle dedicated to the biogenesis of secreted proteins in Streptococcus pyogenes
Author(s) -
Rosch Jason W.,
Caparon Michael G.
Publication year - 2005
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2005.04887.x
Subject(s) - biogenesis , biology , secretory protein , secretion , microbiology and biotechnology , organelle , protein subunit , organelle biogenesis , cysteine protease , secretory pathway , membrane protein , protease , streptococcus pyogenes , biochemistry , endoplasmic reticulum , bacteria , enzyme , genetics , membrane , gene , golgi apparatus , staphylococcus aureus
Summary The Gram‐positive pathogen Streptococcus pyogenes secretes proteins through the ExPortal, a unique single microdomain of the cellular membrane specialized to contain the Sec translocons. It has been proposed that the ExPortal functions as an organelle to promote the biogenesis of secreted proteins by coordinating interactions between nascent unfolded secretory proteins and membrane‐associated chaperones. In this study we provide evidence to support this model. It was found that HtrA (DegP), a surface anchored accessory factor required for maturation of the secreted SpeB cysteine protease, was localized exclusively to the ExPortal. Furthermore, the ATP synthase β subunit was not localized to the ExPortal, suggesting that retention is likely restricted to a specific subset of exported proteins. Mutations that disrupted the anchoring, but not the protease activity, of HtrA, also altered the maturation kinetics of SpeB demonstrating that localization to the ExPortal was important for HtrA function. These data indicate that the ExPortal provides a mechanism by which Gram‐positive bacteria can coordinate protein secretion and subsequent biogenesis in the absence of a specialized protein‐folding compartment.