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Structural consequences of phosphorylation of two serine residues in the cytoplasmic domain of HIV‐1 VpU
Author(s) -
Wittlich Marc,
Koenig Bernd W.,
Willbold Dieter
Publication year - 2008
Publication title -
journal of peptide science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 66
eISSN - 1099-1387
pISSN - 1075-2617
DOI - 10.1002/psc.1004
Subject(s) - phosphorylation , cytoplasm , chemistry , peptide , serine , nuclear magnetic resonance spectroscopy , heteronuclear molecule , biophysics , circular dichroism , conformational change , helix (gastropod) , biochemistry , stereochemistry , biology , ecology , snail
The human immunodeficiency virus type 1 (HIV‐1) protein U (VpU) is an accessory protein responsible for enhancement of viral particle release and down regulation of the T‐lymphocyte coreceptor CD4. Direct binding between the cytoplasmic domains of CD4 and VpU as well as phosphorylation of serines 53 and 57 in the cytoplasmic domain of VpU plays a central role in CD4 downregulation. We investigated structural consequences of phosphorylation of the two serines using nuclear magnetic resonance spectroscopy. A uniformly 15 N and 13 C stable isotope‐labeled 45‐residue peptide comprising the cytoplasmic domain of VpU (VpUcyt) was recombinantly produced in E .coli . The peptide forms two helices (commonly referred to as helix 2 and 3) in the presence of membrane mimicking dodecylphosphocholine (DPC) micelles, which flank a flexible region containing the two phosphorylation sites. Phosphorylation does not cause any drastic structural changes in the secondary structure of VpUcyt. However, an N ‐terminal elongation of helix 3 and a slightly reduced helicity at the C ‐terminus of helix 2 are observed upon phosphorylation based on characteristic changes of 13 C α and 13 C β chemical shifts. Phosphorylation also reduces the local mobility of the protein backbone in the loop region containing the phosphorylation sites according to heteronuclear 1 H 15 N nuclear Overhauser enhancement (NOE) data. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.