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Assessment of Immunologically Relevant Dynamic Tertiary Structural Features of the HIV-1 V3 Loop Crown R2 Sequence by ab initio Folding
Published on: September 16, 2010
Conformational state of a 25-mer peptide from the cyclophilin-binding loop of the HIV type 1 capsid protein
U Reimer1, M Drewello, M Jakob
1Max-Planck-Gesellschaft, Forschungsstelle Enzymologie der Proteinfaltung, Halle/S., Federal Republic of Germany.
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.
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