title: Structure of the pneumococcal l,d-carboxypeptidase DacB and pathophysiological effects of disabled cell wall hydrolases DacA and DacB.
abstract: Bacterial cell wall hydrolases are essential for peptidoglycan turnover and crucial to preserve cell shape. The d,d-carboxypeptidase DacA and l,d-carboxypeptidase DacB of Streptococcus pneumoniae function in a sequential manner. Here, we determined the structure of the surface-exposed lipoprotein DacB. The crystal structure of DacB, radically different to that of DacA, contains a mononuclear Zn(2+) catalytic centre located in the middle of a large and fully exposed groove. Two different conformations were found presenting a different arrangement of the active site topology. The critical residues for catalysis and substrate specificity were identified. Loss-of-function of DacA and DacB altered the cell shape and this was consistent with a modified peptidoglycan peptide composition in dac mutants. Contrary, an lgt mutant lacking lipoprotein diacylglyceryl transferase activity required for proper lipoprotein maturation retained l,d-carboxypeptidase activity and showed an intact murein sacculus. In addition we demonstrated pathophysiological effects of disabled DacA or DacB activities. Real-time bioimaging of intranasal infected mice indicated a substantial attenuation of ΔdacB and ΔdacAΔdacB pneumococci, while ΔdacA had no significant effect. In addition, uptake of these mutants by professional phagocytes was enhanced, while the adherence to lung epithelial cells was decreased. Thus, structural and functional studies suggest DacA and DacB as optimal drug targets.
authors: Department Genetics of Microorganisms, Interfaculty Institute for Genetics and Functional Genomics, Ernst Moritz Arndt University of Greifswald, D-17487, Greifswald, Germany.
authors: Mohammed R
authors: MR
authors: Abdullah
authors: Javier
authors: J
authors: Gutiérrez-Fernández
authors: Thomas
authors: T
authors: Pribyl
authors: Nicolas
authors: N
authors: Gisch
authors: Malek
authors: M
authors: Saleh
authors: Manfred
authors: M
authors: Rohde
authors: Lothar
authors: L
authors: Petruschka
authors: Gerhard
authors: G
authors: Burchhardt
authors: Dominik
authors: D
authors: Schwudke
authors: Juan A
authors: JA
authors: Hermoso
authors: Sven
authors: S
authors: Hammerschmidt
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D002268:Carboxypeptidases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D020134:Catalytic Domain; D002473:Cell Wall / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D051379:Mice; D008958:Models, Molecular; D010641:Phenotype; D011008:Pneumococcal Infections / Q000378:metabolism / Q000662:veterinary*; D017433:Protein Structure, Secondary; D013296:Streptococcus pneumoniae / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity
chemical_list: D001426:Bacterial Proteins; D002268:Carboxypeptidases