Crystal structure of arabidopsis thaliana cyclophilin 38 (AtCyP38)

Abstract

Cyclophilins are proteins that bind to cyclosporin A, an immunosuppressant drug usually administered during organ transplantation, against rejection. These proteins show peptidyl-prolyl isomerase activity, which catalyzes the isomerization of peptidyl-prolyl bonds from the trans form to cis form and facilitates protein folding. In plants, cyclophilins form a significant component of the chloroplast proteome. Cyclophilin 38 (CyP38) is a highly divergent multi-domain cyclophilin from Arabidopsis thaliana. The crystal structure of an intermediate form of AtCyP38 (residues 83-437) has been solved by Multi-wavelength Anomalous Dispersion (MAD) method at 2.46 Angstrom resolution. The structure has two distinct domains; a helical bundle and a cyclophilin domain. A short stretch at the N-terminus of the mature protein is expected to bind to a phosphatase and regulate the dephosphorylation process in the plant Photosystem II. The structure explains how an inactive AtCyP38 intermediate is protected during transportation and mature to form an active protein.