X-ray structure of a decameric cyclophilin-cyclosporin crystal complex

Abstract

Human cyclophilin A (CypA), a ubiquitous intracellular protein of 165 amino acids, is the major receptor for the cyclic undecapeptide immunosuppressant drug cyclosporin A (CsA), which prevents allograft rejection after transplant surgery and is efficacious in the field of autoimmune diseases. CsA prevents T-cell proliferation by blocking the calcium-activated pathway leading to interleukin-2 transcription. Besides their ability to bind CsA, the cyclophilin isoforms also have peptidyl-prolyl isomerase activity and enhance the rate of protein folding. The macrolide FK506 acts similarly to CsA and its cognate receptor FKBP also has peptidyl-prolyl isomerase activity. Inhibition of this enzymatic activity alone is not sufficient to achieve immunosuppression. A direct molecular interaction between the drug-immunophilin complex (CsA-CypA, or FK506-FKBP) and the phosphatase calcineurin, is responsible for modulating the T-cell receptor signal transduction pathway. Here we describe the crystal structure of a decameric CypA-CsA complex. The crystallographic asymmetric unit is composed of a pentamer of 1:1 cyclophilin-cyclosporin complexes of rather exact non-crystallographic fivefold symmetry. The 2.8 A electron density map is of high quality. The five independent cyclosporin molecules are clearly identifiable, providing an unambiguous picture of the detailed interactions between a peptide drug and its receptor. It broadly confirms the results of previous NMR, X-ray and modelling studies, but provides further important structural details which will be of use in the design of drugs that are analogues of CsA.

A Redox 2-Cys Mechanism Regulates the Catalytic Activity of Divergent Cyclophilins

“…The overall architecture of CsCyp is highly similar to that of the C. elegans Cyp3 and human CypA structures in complex with CsA (Pflügl et al, 1993;Ke et al, 1994;Dornan et al, 1999) and comprises an eight-stranded antiparallel b-barrel capped at either end by two a-helices (Fig. 2, A and B).…”

“…The CsCyp active site, composed of 13 residues that are also responsible for CsA binding (Fig. 1A), is identical to that of Cyp3, CypA, and TaCypA-1 (Pflügl et al, 1993;Ke et al, 1994;Dornan et al, 1999;Sekhon et al, 2013). Structure alignment of CsCyp with TaCypA-1, the only other plant divergent Cyp with known threedimensional (3D) structure, showed no major structural differences (root mean square deviation = 0.43 Å).…”

Characterization of a cDNA Encoding a Cytosolic Peptidylprolyl Cis‐Trans ‐Isomerase from Blattella Germanica

“…This analysis reveals a hydrophobic core, which corresponds with the common central region that characterizes these proteins (data not shown). Although the structure of the B. germanicu protein is unknown, it has been determined for cyclophilins from other organisms, both i n an uncomplexed form (Kallen et al, 1991) and complexed with CsA (Pflugl et al, 1993). These proteins have a globular structure that includes eight [j-strands wrapped in antiparallel fashion around a cylinder surface, and two a-helices sitting on the top and on the botton of this cylinder.…”

Cyclophilin‐A is a zinc‐dependent DNA binding protein in macrophages

“…Apparently, zinc binding induces conformational changes of nCyp. We assume the binding site of zinc to be not within the CsA binding pocket of nCyp according to the published data [34] and our computer modelling attempts (unpublished results).…”

“…Additionally, ZnC12 interferes with the binding sites involved in CsA binding of nCyp [34], i.e. we analyzed the [3H]CsA binding of nCyp after zinc treatment.…”