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Crystallization and preliminary X-ray diffraction studies of the pneumococcal teichoic acid phosphorylcholine esterase Pce.

ABSTRACT: The pneumococcal phosphorylcholine esterase (Pce or CbpE) is a modular protein that hydrolyses the phosphorylcholine residues present in the teichoic and lipoteichoic acids of the pneumococcal cell wall. Pce has been crystallized using the hanging-drop vapour-diffusion method at 291 K. Diffraction-quality monoclinic crystals belong to space group C2, with unit-cell parameters a = 169.82, b = 57.26, c = 67.44 A, beta = 112.60 degrees. A 2.7 A resolution SAD data set from a non-isomorphous Gd-HPDO3A Pce derivative was collected at the gadolinium L(III) absorption edge using synchrotron radiation.

SUBMITTER: Lagartera L

PROVIDER: S-EPMC1952259 | biostudies-literature | 2005 Feb

REPOSITORIES: biostudies-literature

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Attachment of phosphorylcholine residues to pneumococcal teichoic acids and modification of substitution patterns by the phosphorylcholine esterase.

Project description:The bacterial lung pathogen Streptococcus pneumoniae has a unique nutritional requirement for exogenous choline and attaches phosphorylcholine (P-Cho) residues to the GalpNAc moieties of its teichoic acids (TAs) in its cell wall. Two phosphorylcholine transferases, LicD1 and LicD2, mediate the attachment of P-Cho to the O-6 positions of the two GalpNAc residues present in each repeating unit of pneumococcal TAs (pnTAs), of which only LicD1 has been determined to be essential. At the molecular level, the specificity of the P-Cho attachment to pnTAs by LicD1 and LicD2 remains still elusive. Here, using detailed structural analyses of pnTAs from a LicD2-deficient strain, we confirmed the specificity in the attachment of P-Cho residues to pnTA. LicD1 solely transfers P-Cho to α-d-GalpNAc moieties, whereas LicD2 attaches P-Cho to β-d-GalpNAc. Further, we investigated the role of the pneumococcal phosphorylcholine esterase (Pce) in the modification of the P-Cho substitution pattern of pnTAs. To clarify the specificity of Pce-mediated P-Cho hydrolysis, we evaluated different concentrations and pH conditions for the treatment of pneumococcal lipoteichoic acid with purified Pce. We show that Pce can hydrolyze both P-Cho residues of the terminal repeat of the pnTA chain and almost all P-Cho residues bound to β-d-GalpNAc in vitro However, hydrolysis in vivo was restricted to the terminal repeat. In summary, our findings indicate that LicD1 and LicD2 specifically transfer P-Cho to α-d-GalpNAc and β-d-GalpNAc moieties, respectively, and that Pce removes distinct P-Cho substituents from pnTAs.

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Pneumococcal phosphorylcholine esterase, Pce, contains a metal binuclear center that is essential for substrate binding and catalysis.

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Phosphorylcholine esterase is critical for Dolichos biflorus and Helix pomatia agglutinin binding to pneumococcal teichoic acid.

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