Biology Faculty Articles

Title

The Yersinia pestis type III secretion needle plays a direct role in the regulation of Yop secretion

Document Type

Article

Publication Date

1-1-2005

Publication Title

Molecular Microbiology

ISSN

0950-382X

Volume

57

Issue/No.

6

First Page

1719

Last Page

1733

Abstract

Activation of bacterial virulence-associated type III secretion systems (T3SSs) requires direct contact between a bacterium and a eukaryotic cell. In Yersinia pestis, the cytosolic LcrG protein and a cytosolic YopN-TyeA complex function to block T3S in the presence of extracellular calcium and prior to contact with a eukaryotic cell. The mechanism by which the bacterium senses extracellular calcium and/or cell contact and transmits these signals to the cytosolic compartment is unknown. We report here that YscF, a small protein that polymerizes to form the external needle of the T3SS, is essential for the calcium-dependent regulation of T3S. Alanine-scanning mutagenesis was used to identify YscF mutants that secrete virulence proteins in the presence and absence of calcium and prior to contact with a eukaryotic cell. Interestingly, one of the YscF mutants that exhibited constitutive T3S was unable to translocate secreted proteins across the eukaryotic plasma membrane. These data indicate that the YscF needle is a multifunctional structure that participates in virulence protein secretion, in translocation of virulence proteins across eukaryotic membranes and in the cell contact- and calcium-dependent regulation of T3S