title: Calmodulin binding properties of peptide analogues and fragments of the calmodulin-binding domain of simian immunodeficiency virus transmembrane glycoprotein 41.
abstract: The calcium-regulatory protein calmodulin (CaM) can bind with high affinity to a region in the cytoplasmic C-terminal tail of glycoprotein 41 of simian immunodeficiency virus (SIV). The amino acid sequence of this region is (1)DLWETLRRGGRW(13)ILAIPRRIRQGLELT(28)L. In this work, we have used near- and far-uv CD, and fluorescence spectroscopy, to study the orientation of this peptide with respect to CaM. We have also studied biosynthetically carbon-13 methyl-Met calmodulin by (1)H, (13)C heteronuclear multiple quantum coherence NMR spectroscopy. Two Trp-substituted peptides, SIV-W3F and SIV-W12F, were utilized in addition to the intact SIV peptide. Two half-peptides, SIV-N (residues 1-13) and SIV-C (residues 13-28) were also synthesized and studied. The spectroscopic results obtained with the SIV-W3F and SIV-W12F peptides were generally consistent with those obtained for the native SIV peptide. Like the native peptide, these two analogues bind with an alpha-helical structure as shown by CD spectroscopy. Fluorescence intermolecular quenching studies suggested binding of Trp3 to the C-lobe of CaM. Our NMR results show that SIV-N can bind to both lobes of calcium-CaM, and that it strongly favors binding to the C-terminal hydrophobic region of CaM. The SIV-C peptide binds with relatively low affinity to both halves of the protein. These data reveal that the intact SIV peptide binds with its N-terminal region to the carboxy-terminal region of CaM, and this interaction initiates the binding of the peptide. This orientation is similar to that of most other CaM-binding domains.
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada.
authors.forename: T
authors.initials: T
authors.lastname: Yuan
authors.forename: S
authors.initials: S
authors.lastname: Tencza
authors.forename: T A
authors.initials: TA
authors.lastname: Mietzner
authors.forename: R C
authors.initials: RC
authors.lastname: Montelaro
authors.forename: H J
authors.initials: HJ
authors.lastname: Vogel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002147:Calmodulin / Q000737:chemistry / Q000378:metabolism*; D002942:Circular Dichroism; D006678:HIV / Q000378:metabolism; D015700:HIV Envelope Protein gp41 / Q000737:chemistry* / Q000378:metabolism*; D000882:Haplorhini; D006801:Humans; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D012191:Retroviridae Proteins / Q000737:chemistry* / Q000378:metabolism*; D015302:Simian Immunodeficiency Virus / Q000378:metabolism; D013050:Spectrometry, Fluorescence
chemical_list: D002147:Calmodulin; D015700:HIV Envelope Protein gp41; D008562:Membrane Glycoproteins; D010446:Peptide Fragments; D012191:Retroviridae Proteins; C082614:SIV envelope protein gp41