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1fgl

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[[Image:1fgl.gif|left|200px]]
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{{STRUCTURE_1fgl| PDB=1fgl | SCENE= }}
{{STRUCTURE_1fgl| PDB=1fgl | SCENE= }}
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'''CYCLOPHILIN A COMPLEXED WITH A FRAGMENT OF HIV-1 GAG PROTEIN'''
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===CYCLOPHILIN A COMPLEXED WITH A FRAGMENT OF HIV-1 GAG PROTEIN===
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==Overview==
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BACKGROUND: 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.
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(as it appears on PubMed at http://www.pubmed.gov), where 9016720 is the PubMed ID number.
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{{ABSTRACT_PUBMED_9016720}}
==About this Structure==
==About this Structure==
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[[Category: Binding protein for cyclosporin some]]
[[Category: Binding protein for cyclosporin some]]
[[Category: Cyclophilin]]
[[Category: Cyclophilin]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 03:13:07 2008''

Revision as of 00:13, 1 July 2008

Image:1fgl.png

Template:STRUCTURE 1fgl

CYCLOPHILIN A COMPLEXED WITH A FRAGMENT OF HIV-1 GAG PROTEIN

Template:ABSTRACT PUBMED 9016720

About this Structure

1FGL is a Protein complex structure of sequences from Homo sapiens. Full crystallographic information is available from OCA.

Reference

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

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