Two Distinct Regions of Cyclophilin B Are Involved in the Recognition of a Functional Receptor and of Glycosaminoglycans on T Lymphocytes

• Published in: The Journal of biological chemistry Vol. 274; no. 16; pp. 10990 - 10998
• Main Authors: Carpentier, M, Allain, F, Haendler, B, Denys, A, Mariller, C, Benaïssa, M, Spik, G
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 16.04.1999
• Subjects: Amino Acid Sequence; Binding Sites; Cyclophilins; Glycosaminoglycans - metabolism; Humans; Immunophilins - chemistry; Immunophilins - genetics; Immunophilins - metabolism; Jurkat Cells; Models, Molecular; Molecular Sequence Data; Mutagenesis, Site-Directed; Peptidylprolyl Isomerase; Protein Binding; Protein Conformation; Sequence Homology, Amino Acid; T-Lymphocytes - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.16.10990

Cyclophilin B is a cyclosporin A-binding protein exhibiting peptidyl-prolyl cis/trans isomerase activity. We have previously shown that it interacts with two types of binding sites on T lymphocytes. The type I sites correspond to specific functional receptors and the type II sites to sulfated glycosaminoglycans. The interactions of cyclophilin B with type I and type II sites are reduced in the presence of cyclosporin A and of a synthetic peptide mimicking the N-terminal part of cyclophilin B, respectively, suggesting that the protein possesses two distinct binding regions. In this study, we intended to characterize the areas of cyclophilin B involved in the interactions with binding sites present on Jurkat cells. The use of cyclophilin B mutants modified in the N-terminal region demonstrated that the 3 Lys-Lys-Lys 5 and 14 Tyr-Phe-Asp 16 clusters are probably solely required for the interactions with the type II sites. We further engineered mutants of the conserved central core of cyclophilin B, which bears the catalytic and the cyclosporin A binding sites as an approach to localize the binding regions for the type I sites. The enzymatic activity of cyclophilin B was dramatically reduced after substitution of the Arg 62 and Phe 67 residues, whereas the cyclosporin A binding activity was destroyed by mutation of the Trp 128 residue and strongly decreased after modification of the Phe 67 residue. Only the substitution of the Trp 128 residue reduced the binding of the resulting cyclophilin B mutant to type I binding sites. The catalytic site of cyclophilin B therefore did not seem to be essential for cellular binding and the cyclosporin A binding site appeared to be partially involved in the binding to type I sites.