A family of lysozyme-like virulence factors in bacterial pathogens of plants and animals

• Published in: Proceedings of the National Academy of Sciences - PNAS 1996-07, Vol.93 (14), p.7321-7326
• Main Authors: Mushegian, A.R. (University of Washington, Seattle, WA.), Fullner, K.J, Koonin, E.V, Nester, E.W
• Format: Article
• Language: English
• Subjects: Agrobacterium; AGROBACTERIUM TUMEFACIENS; Amino Acid Sequence; Animals; BACTERIA; Bacteria - pathogenicity; Bacterial Proteins - chemistry; CHANCRE; Chickens; Conserved Sequence; DNA; ENZIMAS; ENZYME; Female; Geese; Genes; GLICOSIDOS; GLYCOSIDE; Information search; Inoculation; KALANCHOE; LISOZIMA; LYSOZYME; Microbiology; Models, Structural; Molecular Sequence Data; Muramidase - chemistry; MUTACION; MUTANT; MUTANTES; MUTATION; NECROSIS CANCEROSA; NEOPLASMAS; NEOPLASME; PATOGENICIDAD; Plant Tumors; Plants - microbiology; Plasmids; POLLO; POULET; POUVOIR PATHOGENE; Protein Structure, Secondary; PROTEINAS; PROTEINE; Proteins; Rhizobium - genetics; Rhizobium - pathogenicity; SALMONELLA; Salmonella - pathogenicity; Salmonella enterica; SECUENCIA NUCLEOTIDICA; Sequence Homology, Amino Acid; SEQUENCE NUCLEOTIDIQUE; SHIGELLA; Shigella - pathogenicity; Three dimensional modeling; Tumors; Virulence; Virulence Factors
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.93.14.7321

We describe a conserved family of bacterial gene products that includes the VirB1 virulence factor encoded by tumor-inducing plasmids of Agrobacterium spp., proteins involved in conjugative DNA transfer of broad-hostrange bacterial plasmids, and gene products that may be involved in invasion by Shigella spp. and Salmonella enterica. Sequence analysis and structural modeling show that the proteins in this group are related to chicken egg white lysozyme and are likely to adopt a lysozyme-like structural fold. Based on their similarity to lysozyme, we predict that these proteins have glycosidase activity. Iterative data base searches with three conserved sequence motifs from this protein family detect a more distant relationship to bacterial and bacteriophage lytic transglycosylases, and goose egg white lysozyme. Two acidic residues in the VirB1 protein of Agrobacterium tumefaciens form a putative catalytic dyad. Each of these residues was changed into the corresponding amide by site-directed mutagenesis. Strains of A. tumefaciens that express mutated VirB1 proteins have a significantly reduced virulence. We hypothesize that many bacterial proteins involved in export of macromolecules belong to a widespread class of hydrolases and cleave beta-1,4-glycosidic bonds as part of their function