Crystallization of the Non-catalytic Domain of YopH from Yersinia pseudotuberculosis. Craig L. Smith, James B. Bliska*, and Mark A. Saper, Department of Biological Chemistry and Biophysics Research Division, The University of Michigan, Ann Arbor, MI 48109, *Department of Molecular Genetics and Microbiology, State University of New York at Stony Brook, Stony Brook, NY 11794

Bacteria of the genus Yersinia cause a wide variety of diseases in humans and rodents ranging from gastroenteritis to the bubonic plague. Virulence genes found on a 70 kb plasmid encode a recently characterized type III secretion system that injects virulent proteins into host cells. Unlike other Gram-negative secretion pathways, bacteria that possess this system are able to directly deliver virulence factors to the host cell without being accessible to the host immune defenses. Type III secretion systems have been found in a variety of other plant and animal pathogenic bacteria suggesting that a common motif for the transfer of virulence proteins from bacterium to host.

Yersinia secretes YopH, a potent tyrosine phosphatase, into host macrophages by type III secretion. The phosphatase dephosporylates specific host proteins, suppresses phagocytosis and allows the bacteria to evade the primary immune response. Experimental evidence suggests that motifs responsible for secretion and translocation are located in the first 71 residues of YopH. Interestingly, the amino-terminal region of YopH shows strong homology to another plasmid-encoded protein called LcrQ, which has been shown to be a concentration-dependent repressor of virulence protein secretion.

Our lab previously has solved the crystal structure of the catalytic domain (163-468) to 2.5 Å resolution. We now have crystallized the amino-terminal domain (1-129). Crystals diffract to at least 2.5 Å and belong to the orthorhombic space group C222 with unit cell parameters a=48.2 Å, b=121.7 Å, c=49.1 Å. Heavy atom screening is now in progress.