title: Structure and cell wall cleavage by modular lytic transglycosylase MltC of Escherichia coli.
abstract: The lytic transglycosylases are essential bacterial enzymes that catalyze the nonhydrolytic cleavage of the glycan strands of the bacterial cell wall. We describe here the structural and catalytic properties of MltC, one of the seven lytic transglycosylases found in the genome of the Gram-negative bacterium Escherichia coli. The 2.3 Å resolution X-ray structure of a soluble construct of MltC shows a unique, compared to known lytic transglycosylase structures, two-domain structure characterized by an expansive active site of 53 Å length extending through an interface between the domains. The structures of three complexes of MltC with cell wall analogues suggest the positioning of the peptidoglycan in the active site both as a substrate and as a product. One complex is suggested to correspond to an intermediate in the course of sequential and exolytic cleavage of the peptidoglycan. Moreover, MltC partitioned its reactive oxocarbenium-like intermediate between trapping by the C6-hydroxyl of the muramyl moiety (lytic transglycosylase activity, the major path) and by water (muramidase activity). Genomic analysis identifies the presence of an MltC homologue in no less than 791 bacterial genomes. While the role of MltC in cell wall assembly and maturation remains uncertain, we propose a functional role for this enzyme as befits the uniqueness of its two-domain structure.
authors.affiliation: Department of Crystallography and Structural Biology, Inst. Química-Física "Rocasolano", CSIC , Serrano 119, 28006 Madrid, Spain.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Artola-Recolons
authors.forename: Mijoon
authors.initials: M
authors.lastname: Lee
authors.forename: Noelia
authors.initials: N
authors.lastname: Bernardo-García
authors.forename: Blas
authors.initials: B
authors.lastname: Blázquez
authors.forename: Dusan
authors.initials: D
authors.lastname: Hesek
authors.forename: Sergio G
authors.initials: SG
authors.lastname: Bartual
authors.forename: Kiran V
authors.initials: KV
authors.lastname: Mahasenan
authors.forename: Elena
authors.initials: E
authors.lastname: Lastochkin
authors.forename: Hualiang
authors.initials: H
authors.lastname: Pi
authors.forename: Bill
authors.initials: B
authors.lastname: Boggess
authors.forename: Kathrin
authors.initials: K
authors.lastname: Meindl
authors.forename: Isabel
authors.initials: I
authors.lastname: Usón
authors.forename: Jed F
authors.initials: JF
authors.lastname: Fisher
authors.forename: Shahriar
authors.initials: S
authors.lastname: Mobashery
authors.forename: Juan A
authors.initials: JA
authors.lastname: Hermoso
mesh_terms: D020134:Catalytic Domain; D002473:Cell Wall / Q000378:metabolism; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000166:cytology / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016695:Glycosyltransferases / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation; D010457:Peptidoglycan / Q000737:chemistry; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
chemical_list: D029968:Escherichia coli Proteins; D010457:Peptidoglycan; D016695:Glycosyltransferases; C000601709:MltC protein, E coli