title: Crystal structure of phosphorylcholine esterase domain of the virulence factor choline-binding protein e from streptococcus pneumoniae: new structural features among the metallo-beta-lactamase superfamily.
abstract: Streptococcus pneumoniae is the worldwide leading cause of deaths from invasive infections such as pneumoniae, sepsis, and meningitidis in children and the elderly. Nasopharyngeal colonization, which plays a key role in the development of pneumococcal disease, is highly dependent on a family of surface-exposed proteins, the choline-binding proteins (CBPs). Here we report the crystal structure of phosphorylcholine esterase (Pce), the catalytic domain of choline-binding protein E (CBPE), which has been shown to be crucial for host/pathogen interaction processes. The unexpected features of the Pce active site reveal that this enzyme is unique among the large family of hydrolases harboring the metallo-beta-lactamase fold. The orientation and calcium stabilization features of an elongated loop, which lies on top of the active site, suggest that the cleft may be rearranged. Furthermore, the structure of Pce complexed with phosphorylcholine, together with the characterization of the enzymatic role played by two iron ions located in the active site allow us to propose a reaction mechanism reminiscent of that of purple acid phosphatase. This mechanism is supported by site-directed mutagenesis experiments. Finally, the interactions of the choline binding domain and the Pce region of CBPE with chains of teichoic acids have been modeled. The ensemble of our biochemical and structural results provide an initial understanding of the function of CBPE.
authors.affiliation: Laboratoire de Cristallographie Macromoléculaire, Institut de Biologie Structurale Jean-Pierre Ebel (CEA-CNRS UMR 5075-UJF), 41 Rue Jules Horowitz 38027, Grenoble Cedex 1, France.
authors.forename: Gianpiero
authors.initials: G
authors.lastname: Garau
authors.forename: David
authors.initials: D
authors.lastname: Lemaire
authors.forename: Thierry
authors.initials: T
authors.lastname: Vernet
authors.forename: Otto
authors.initials: O
authors.lastname: Dideberg
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: Di Guilmi
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry / Q000378:metabolism*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D013296:Streptococcus pneumoniae / Q000201:enzymology* / Q000472:pathogenicity*; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D002265:Carboxylic Ester Hydrolases; C022718:teichoic acid phosphorylcholine esterase