title: New sub-family of lysozyme-like proteins shows no catalytic activity: crystallographic and biochemical study of STM3605 protein from Salmonella Typhimurium.
abstract: Phage viruses that infect prokaryotes integrate their genome into the host chromosome; thus, microbial genomes typically contain genetic remnants of both recent and ancient phage infections. Often phage genes occur in clusters of atypical G+C content that reflect integration of the foreign DNA. However, some phage genes occur in isolation without other phage gene neighbors, probably resulting from horizontal gene transfer. In these cases, the phage gene product is unlikely to function as a component of a mature phage particle, and instead may have been co-opted by the host for its own benefit. The product of one such gene from Salmonella enterica serovar Typhimurium, STM3605, encodes a protein with modest sequence similarity to phage-like lysozyme (N-acetylmuramidase) but appears to lack essential catalytic residues that are strictly conserved in all lysozymes. Close homologs in other bacteria share this characteristic. The structure of the STM3605 protein was characterized by X-ray crystallography, and functional assays showed that it is a stable, folded protein whose structure closely resembles lysozyme. However, this protein is unlikely to hydrolyze peptidoglycan. Instead, STM3605 is presumed to have evolved an alternative function because it shows some lytic activity and partitions to micelles.
authors.affiliation: The Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory, Argonne, IL, USA.
authors.forename: Karolina
authors.initials: K
authors.lastname: Michalska
authors.forename: Roslyn N
authors.initials: RN
authors.lastname: Brown
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.forename: Robert
authors.initials: R
authors.lastname: Jedrzejczak
authors.forename: George S
authors.initials: GS
authors.lastname: Niemann
authors.forename: Fred
authors.initials: F
authors.lastname: Heffron
authors.forename: John R
authors.initials: JR
authors.lastname: Cort
authors.forename: Joshua N
authors.initials: JN
authors.lastname: Adkins
authors.forename: Gyorgy
authors.initials: G
authors.lastname: Babnigg
authors.forename: Andrzej
authors.initials: A
authors.lastname: Joachimiak
mesh_terms: D000595:Amino Acid Sequence; D001407:Bacillus / Q000187:drug effects; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001435:Bacteriophages / Q000235:genetics* / Q000378:metabolism; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000235:genetics; D022761:Gene Transfer, Horizontal; D007700:Kinetics; D008823:Micelles; D016982:Micrococcus luteus / Q000187:drug effects; D008969:Molecular Sequence Data; D009113:Muramidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D017510:Protein Folding; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012486:Salmonella typhimurium / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D008823:Micelles; D020033:Protein Isoforms; D011994:Recombinant Proteins; D009113:Muramidase