title: BiP-binding sequences in HIV gp160. Implications for the binding specificity of bip.
abstract: BiP, a resident endoplasmic reticulum member of the HSP70 family of molecular chaperones, associates transiently with a wide variety of newly synthesized exocytotic proteins. In addition to immunoglobulin heavy and light chains, the first natural substrates identified for BiP, a number of viral polypeptides including the human immunodeficiency virus type 1 envelope glycoprotein gp160 interact with BiP during their passage through the endoplasmic reticulum. We have used a computer algorithm developed to predict BiP-binding sites within protein primary sequences to identify sites within gp160 that might mediate its association with BiP. Analysis of the ability of 22 synthetic heptapeptides corresponding to predicted binding sites to stimulate the ATPase activity of BiP or to compete with an unfolded polypeptide for binding to BiP indicated that about half of them are indeed recognized by the chaperone. All of the confirmed binding sites are localized within conserved regions of gp160, suggesting a conserved role for BiP in the folding of gp160. Information on the characteristics of confirmed BiP-binding peptides gained in this and previous studies has been utilized to improve the predictive power of the BiP Score algorithm and to investigate the differences in peptide binding specificities of HSP70 family members.
authors.affiliation: Institut für Biophysik & Physikalische Biochemie, Universität Regensburg, 93040 Regensburg, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Knarr
authors.forename: S
authors.initials: S
authors.lastname: Modrow
authors.forename: A
authors.initials: A
authors.lastname: Todd
authors.forename: M J
authors.initials: MJ
authors.lastname: Gething
authors.forename: J
authors.initials: J
authors.lastname: Buchner
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D004789:Enzyme Activation; D019302:HIV Envelope Protein gp160 / Q000737:chemistry / Q000378:metabolism*; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D019302:HIV Envelope Protein gp160; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D011994:Recombinant Proteins; D000251:Adenosine Triphosphatases