Abstract
LcrV, a multifunctional protein, acts as a positive regulator of effector protein secretion for the type III secretion system (T3SS) in Yersinia pestis by interaction with the negative regulator LcrG. In this study, LcrV was analyzed to identify regions required for LcrG interaction. Random-linker insertion mutagenesis, deletion analysis, and site-directed mutagenesis of hydrophobic amino acids between residues 290 and 311 allowed the isolation of an LcrV mutant (LcrV L291R F308R) defective for LcrG interaction. The new residues identified in LcrG interaction lie in helix 12 of LcrV; residues in helix 7 of LcrV are known to be involved in LcrG interaction. Helix 7 and helix 12 of LcrV interact to form an intramolecular coiled coil; these new results suggest that the intramolecular coiled coil in LcrV is required for LcrG interaction and activation of the T3SS.