title: Tat peptide-calmodulin binding studies and bioinformatics of HIV-1 protein-calmodulin interactions.
abstract: The human immunodeficiency virus type 1 (HIV-1) genome encodes 18 proteins and 2 peptides. Four of these proteins encode high-affinity calmodulin-binding sites for which direct interactions with calmodulin have already been described. In this study, the HIV-1 proteome is queried using an algorithm that predicts calmodulin-binding sites revealing seven new putative calmodulin-binding sites including residues 34-56 of the transactivator of transcription (Tat). Tat is a 101-residue intrinsically disordered RNA-binding protein that plays a central role in the regulation of HIV-1 replication. Interactions between a Tat peptide (residues 34-56), melittin, a well-characterized calmodulin-binding peptide, and calmodulin were examined by direct binding studies, mass spectrometry, and fluorescence. The Tat peptide binds to both calcium-saturated and apo-calmodulin with a low micromolar affinity. Conformational changes induced in the Tat peptide were determined by circular dichroism, and residues in calmodulin that interact with the peptide were identified by HSQC NMR spectroscopy. Multiple interactions between HIV-1 proteins and calmodulin, a highly promiscuous signal transduction hub protein, may be an important mechanism by which the virus controls cell physiology.
authors.affiliation: Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2.
authors.forename: Peter
authors.initials: P
authors.lastname: McQueen
authors.forename: Lynda J
authors.initials: LJ
authors.lastname: Donald
authors.forename: Thach N
authors.initials: TN
authors.lastname: Vo
authors.forename: Dung H
authors.initials: DH
authors.lastname: Nguyen
authors.forename: Heather
authors.initials: H
authors.lastname: Griffiths
authors.forename: Shaheen
authors.initials: S
authors.lastname: Shojania
authors.forename: Kenneth G
authors.initials: KG
authors.lastname: Standing
authors.forename: Joe D
authors.initials: JD
authors.lastname: O'Neil
mesh_terms: D000595:Amino Acid Sequence; D002147:Calmodulin / Q000737:chemistry / Q000378:metabolism*; D002942:Circular Dichroism; D019295:Computational Biology; D054298:Human Immunodeficiency Virus Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry; D008555:Melitten; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000737:chemistry / Q000378:metabolism*
chemical_list: D002147:Calmodulin; D054298:Human Immunodeficiency Virus Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus; D008555:Melitten