3la6

Publication Abstract from PubMed

Capsular polysaccharides are well-established virulence factors of pathogenic bacteria. Their biosynthesis and export are regulated within the transmembrane polysaccharide assembly machinery by the autophosphorylation of atypical tyrosine-kinases, named BY-kinases. However, the accurate functioning of these tyrosine-kinases remains unknown. Here, we report the crystal structure of the non-phosphorylated cytoplasmic domain of the tyrosine-kinase Wzc from Escherichia coli in complex with ADP showing that it forms a ring-shaped octamer. Mutational analysis demonstrates that a conserved EX(2)RX(2)R motif involved in subunit interactions is essential for polysaccharide export. We also elucidate the role of a putative internal regulatory tyrosine and we show that BY-kinases from proteobacteria autophosphorylate on their C-terminal tyrosine cluster via a single step intermolecular mechanism. This structure-function analysis also allows us to demonstrate that two different parts of a conserved basic region called the RK-cluster are essential for polysaccharide export and for kinase activity, respectively. Based on these data, we revisit the dichotomy made between BY-kinases from proteobacteria and firmicutes and we propose a unique process of oligomerization and phosphorylation. We also reassess the function of BY-kinases in the capsular polysaccharide assembly machinery.

Identification of structural and molecular determinants of the tyrosine-kinase Wzc and implications in capsular polysaccharide export.,Bechet E, Gruszczyk J, Terreux R, Gueguen-Chaignon V, Vigouroux A, Obadia B, Cozzone AJ, Nessler S, Grangeasse C Mol Microbiol. 2010 Jul 13. PMID:20633230^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.