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Structural models for the complex of chemotaxis inhibitory protein of Staphylococcus aureus with the C5a receptor.

ABSTRACT: The study presents structural models for the complex of the chemotaxis inhibitory protein of Staphylococcus aureus, CHIPS, and receptor for anaphylotoxin C5a, C5aR. The models are based on the recently found NMR structure of the complex between CHIPS fragment 31-121 and C5aR fragment 7-28, as well as on previous results of molecular modeling of C5aR. Simple and straightforward modeling procedure selected low-energy conformations of the C5aR fragment 8-41 that simultaneously fit the NMR structure of the C5aR 10-18 fragment and properly orient the NMR structure of CHIPS(31-121) relative to C5aR. Extensive repacking of the side chains of CHIPS(31-121) and C5aR(8-41) predicted specific residue-residue interactions on the interface between CHIPS and C5aR. Many of these interactions were rationalized with experimental data obtained by site-directed mutagenesis of CHIPS and C5aR. The models correctly showed that CHIPS binds only to the first binding site of C5a to C5aR not competing with C5a fragment 59-74, which binds the second binding site of C5aR. The models also predict that two elements of CHIPS, fragments 48-58 and 97-111, may be used as structural templates for potential inhibitors of C5a.

SUBMITTER: Nikiforovich GV

PROVIDER: S-EPMC2787753 | biostudies-literature | 2009 Dec

REPOSITORIES: biostudies-literature

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Structural models for the complex of chemotaxis inhibitory protein of Staphylococcus aureus with the C5a receptor.

Nikiforovich Gregory V GV Baranski Thomas J TJ

Biochemical and biophysical research communications 20090930 3

The study presents structural models for the complex of the chemotaxis inhibitory protein of Staphylococcus aureus, CHIPS, and receptor for anaphylotoxin C5a, C5aR. The models are based on the recently found NMR structure of the complex between CHIPS fragment 31-121 and C5aR fragment 7-28, as well as on previous results of molecular modeling of C5aR. Simple and straightforward modeling procedure selected low-energy conformations of the C5aR fragment 8-41 that simultaneously fit the NMR structure ...[more]

PMID: 19799858

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Project description:BackgroundThe Chemotaxis inhibitory protein of Staphylococcus aureus (CHIPS) blocks the Complement fragment C5a receptor (C5aR) and formylated peptide receptor (FPR) and is thereby a potent inhibitor of neutrophil chemotaxis and activation of inflammatory responses. The majority of the healthy human population has antibodies against CHIPS that have been shown to interfere with its function in vitro. The aim of this study was to define potential epitopes for human antibodies on the CHIPS surface. We also initiate the process to identify a mutated CHIPS molecule that is not efficiently recognized by preformed anti-CHIPS antibodies and retains anti-inflammatory activity.ResultsIn this paper, we panned peptide displaying phage libraries against a pool of CHIPS specific affinity-purified polyclonal human IgG. The selected peptides could be divided into two groups of sequences. The first group was the most dominant with 36 of the 48 sequenced clones represented. Binding to human affinity-purified IgG was verified by ELISA for a selection of peptide sequences in phage format. For further analysis, one peptide was chemically synthesized and antibodies affinity-purified on this peptide were found to bind the CHIPS molecule as studied by ELISA and Surface Plasmon Resonance. Furthermore, seven potential conformational epitopes responsible for antibody recognition were identified by mapping phage selected peptide sequences on the CHIPS surface as defined in the NMR structure of the recombinant CHIPS31-121 protein. Mapped epitopes were verified by in vitro mutational analysis of the CHIPS molecule. Single mutations introduced in the proposed antibody epitopes were shown to decrease antibody binding to CHIPS. The biological function in terms of C5aR signaling was studied by flow cytometry. A few mutations were shown to affect this biological function as well as the antibody binding.ConclusionConformational epitopes recognized by human antibodies have been mapped on the CHIPS surface and amino acid residues involved in both antibody and C5aR interaction could be defined. This information has implications for the development of an effective anti-inflammatory agent based on a functional CHIPS molecule with low interaction with human IgG.

Dataset Information

Structural models for the complex of chemotaxis inhibitory protein of Staphylococcus aureus with the C5a receptor.

Publications

Structural models for the complex of chemotaxis inhibitory protein of Staphylococcus aureus with the C5a receptor.

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