Cyclophilins constitute a ubiquitous protein family whose functions include protein folding, transport and signaling. They possess both sequence-specific binding and proline cis-trans isomerase activities, as exemplified by the interaction between cyclophilin A (CypA) and the HIV-1 CA protein. Here, we report crystal structures of CypA in complex with HIV-1 CA protein variants that bind preferentially with the substrate proline residue in either the cis or the trans conformation. Cis- and trans-Pro substrates are accommodated within the enzyme active site by rearrangement of their N-terminal residues and with minimal distortions in the path of the main chain. CypA Arg55 guanidinium group probably facilitates catalysis by anchoring the substrate proline oxygen and stabilizing sp3 hybridization of the proline nitrogen in the transition state.
Structural insights into the catalytic mechanism of cyclophilin A.,Howard BR, Vajdos FF, Li S, Sundquist WI, Hill CP Nat Struct Biol. 2003 Jun;10(6):475-81. PMID:12730686
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
↑ Howard BR, Vajdos FF, Li S, Sundquist WI, Hill CP. Structural insights into the catalytic mechanism of cyclophilin A. Nat Struct Biol. 2003 Jun;10(6):475-81. PMID:12730686 doi:http://dx.doi.org/10.1038/nsb927