title: Nef of HIV-1 interacts directly with calcium-bound calmodulin.
abstract: It was recently found that the myristoyl group of CAP-23/NAP-22, a neuron-specific protein kinase C substrate, is essential for the interaction between the protein and Ca(2+)-bound calmodulin (Ca(2+)/CaM). Based on the N-terminal amino acid sequence alignment of CAP-23/NAP-22 and other myristoylated proteins, including the Nef protein from human immunodeficiency virus (HIV), we proposed a new hypothesis that the protein myristoylation plays important roles in protein-calmodulin interactions. To investigate the possibility of direct interaction between Nef and calmodulin, we performed structural studies of Ca(2+)/CaM in the presence of a myristoylated peptide corresponding to the N-terminal region of Nef. The dissociation constant between Ca(2+)/CaM and the myristoylated Nef peptide was determined to be 13.7 nM by fluorescence spectroscopy analyses. The NMR experiments indicated that the chemical shifts of some residues on and around the hydrophobic clefts of Ca(2+)/CaM changed markedly in the Ca(2+)/CaM-Nef peptide complex with the molar ratio of 1:2. Correspondingly, the radius of gyration determined by the small angle X-ray scattering measurements is 2-3 A smaller that of Ca(2+)/CaM alone. These results demonstrate clearly that Nef interacts directly with Ca(2+)/CaM.
authors.affiliation: Division of Biomedical Polymer Science, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Aichi 470-1192, Japan. nhayashi@fujita-hu.ac.jp
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Hayashi
authors.forename: Mamoru
authors.initials: M
authors.lastname: Matsubara
authors.forename: Yuji
authors.initials: Y
authors.lastname: Jinbo
authors.forename: Koiti
authors.initials: K
authors.lastname: Titani
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Izumi
authors.forename: Norio
authors.initials: N
authors.lastname: Matsushima
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000737:chemistry / Q000378:metabolism*; D015693:Gene Products, nef / Q000737:chemistry / Q000378:metabolism*; D015497:HIV-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D011485:Protein Binding; D054311:nef Gene Products, Human Immunodeficiency Virus
chemical_list: D002147:Calmodulin; D015693:Gene Products, nef; D054311:nef Gene Products, Human Immunodeficiency Virus; D002118:Calcium