Conformational state of a 25-mer peptide from the cyclophilin-binding loop of the HIV type 1 capsid protein

Biochem J. 1997 Aug 15;326 ( Pt 1)(Pt 1):181-5. doi: 10.1042/bj3260181.

Abstract

Recently a 25-residue part of Gag polyprotein from HIV type 1 (HIV-1) was reported to bind to the cytosolic 18 kDa cyclophilin (Cyp18) with an IC50 value of 180 microM. This peptide corresponds to the Cyp18-binding domain of HIV-1 Gag. A replacement of Gly with Ala in the cyclophilin-binding loop of HIV-1 Gag polyprotein results in the prevention of the packaging of Cyp18 into virions. We found only two conformers of this peptide among 16 possible expected conformers, owing to cis/trans isomerization of four peptidyl-prolyl bonds. Although this finding implicates the existence of a stabilizing structure, we were not able to detect secondary structure formation by 1H-NMR and CD spectroscopy. We characterized the peptide as a substrate for Cyp18 by two-dimensional exchange 1H-NMR spectroscopy. Surprisingly, we found similar binding characteristics for a peptide corresponding to 25-mer peptide containing the above-mentioned Gly to Ala substitution.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Capsid / chemistry*
  • Capsid / metabolism
  • HIV Core Protein p24 / chemistry*
  • HIV Core Protein p24 / metabolism
  • Humans
  • Magnetic Resonance Spectroscopy
  • Methionine
  • Molecular Sequence Data
  • Norleucine
  • Peptide Fragments / chemical synthesis
  • Peptide Fragments / chemistry*
  • Peptide Fragments / metabolism
  • Peptidylprolyl Isomerase / metabolism*
  • Protein Binding
  • Protein Conformation*
  • Solutions

Substances

  • HIV Core Protein p24
  • Peptide Fragments
  • Solutions
  • Norleucine
  • Methionine
  • Peptidylprolyl Isomerase