1. Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut 06536, USA

Correspondence to: Jorge E. Galán¹ Correspondence and requests for materials should be addressed to J.E.G. (Email: jorge.galan@yale.edu).

Abstract

Type III protein secretion systems are essential virulence factors of many bacteria pathogenic to humans, animals and plants¹. These systems mediate the transfer of bacterial virulence proteins directly into the host cell cytoplasm. Proteins are thought to travel this pathway in a largely unfolded manner, and a family of customized cytoplasmic chaperones, which specifically bind cognate secreted proteins, are essential for secretion. Here we show that InvC, an ATPase associated with a Salmonella enterica type III secretion system², has a critical function in substrate recognition. Furthermore, InvC induces chaperone release from and unfolding of the cognate secreted protein in an ATP-dependent manner. Our results show a similarity between the mechanisms of substrate recognition by type III protein secretion systems and AAA + ATPase disassembly machines.

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