1fgl
Cyclophilin A complexed with a fragment of HIV-1 GAG protein
Structural highlights
FunctionPPIA_HUMAN PPIases accelerate the folding of proteins. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBACKGROUND: Cyclophilin A (CyPA), a receptor of the immunosuppressive drug cyclosporin A, catalyzes the cis-trans isomerization of peptidyl-prolyl bonds and is required for the infectious activity of human immunodeficiency virus type 1 (HIV-1). The crystal structure of CyPA complexed with a fragment of the HIV-1 gag protein should provide insights into the nature of CyPA-gag interactions and may suggest a role for CyPA in HIV-1 infectious activity. RESULTS: The crystal structure of CyPA complexed with a 25 amino acid peptide of HIV-1 gag capsid protein (25-mer) was determined and refined to an R factor of 0.195 at 1.8 A resolution. The sequence Ala88-Gly89-Pro90-Ile91 of the gag fragment is the major portion to bind to the active site of CyPA. Two residues of the 25-mer (Pro90-Ile91) bind to CyPA in a similar manner to two residues (Pro-Phe) of the CyPA substrate, succinyl-Ala-Ala-Pro-Phe-p-nitroanilide (AAPF). However, the N-terminus of the 25-mer (Ala88-Gly89) exhibits a different hydrogen-bonding pattern and molecular conformation than AAPF. The peptidyl-prolyl bond between Gly89 and Pro90 of the 25-mer has a trans conformation, in contrast to the cis conformation observed in other known CyPA-peptide complexes. The residue preceding proline, Gly89, has an unfavorable backbone conformation usually only adopted by glycine. CONCLUSIONS: The unfavorable backbone conformation of Gly89 of the gag 25-mer fragment suggests that binding between HIV-1 gag protein and CyPA requires a special sequence, Gly-Pro. Thus, in HIV-1 infectivity, CyPA is likely to function as a chaperone, rather than as a cis-trans isomerase. However, the observation of similarities between the C termini of the 25-mer and the substrate AAPF means that the involvement of the cis-trans isomerase activity of CyPA cannot be completely ruled out. Cyclophilin A complexed with a fragment of HIV-1 gag protein: insights into HIV-1 infectious activity.,Zhao Y, Chen Y, Schutkowski M, Fischer G, Ke H Structure. 1997 Jan 15;5(1):139-46. PMID:9016720[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences | ||||||||||||||||||||
