title: Chromosome-encoded beta-lactamases TUS-1 and MUS-1 from Myroides odoratus and Myroides odoratimimus (formerly Flavobacterium odoratum), new members of the lineage of molecular subclass B1 metalloenzymes.
abstract: Myroides odoratus and Myroides odoratimimus (formerly designated in a single species as Flavobacterium odoratum) are gram-negative aerobes and sources of nosocomial infections in humans. They have variable susceptibility to beta-lactams and a decreased susceptibility to carbapenems. Using genomic DNAs of M. odoratus CIP 103105 and M. odoratimimus CIP 103073 reference strains, shotgun cloning of beta-lactamase genes was performed, followed by protein expression in Escherichia coli. The deduced amino acid sequences of these beta-lactamase genes revealed that TUS-1 and MUS-1 from M. odoratus CIP 103105 and M. odoratimimus CIP 103073, respectively, shared 73% amino acid identity. Mature proteins TUS-1 and MUS-1, with pI values of 7.8 and 5.2, respectively, had relative molecular masses of ca. 26 kDa. These beta-lactamases are members of the subclass B1 of metallo-beta-lactamases and are distantly related to other metalloenzymes, being most closely related to IND-1 from Chryseobacterium indologenes (42% amino acid identity). However, phylogenic analysis showed that TUS-1 and MUS-1 belong to the same phylogenic lineage of subclass B1 enzymes that groups the subclass B1 beta-lactamases of Flavobacterium species. Kinetic parameters of purified beta-lactamases TUS-1 and MUS-1 detailed their hydrolysis spectra, which encompass most beta-lactams except aztreonam. beta-Lactamases TUS-1 and MUS-1 were classified in functional subgroup 3a of metalloenzymes. This work further characterizes chromosome-encoded metalloenzymes from Flavobacteriaceae species that explain at least part of their intrinsic resistance to beta-lactams.
authors.affiliation: Service de Bactériologie-Virologie, Hôpital de Bicêtre, Assistance Publique/Hôpitaux de Paris, Faculté de Médecine Paris-Sud, 94275 Le Kremlin-Bicêtre Cédex, France.
authors.forename: Hedi
authors.initials: H
authors.lastname: Mammeri
authors.forename: Samuel
authors.initials: S
authors.lastname: Bellais
authors.forename: Patrice
authors.initials: P
authors.lastname: Nordmann
mesh_terms: D000595:Amino Acid Sequence; D015139:Blotting, Southern; D002876:Chromosomes, Bacterial / Q000201:enzymology / Q000235:genetics*; D003001:Cloning, Molecular; D003227:Conjugation, Genetic; D005417:Flavobacterium / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D001618:beta-Lactamases