title: Identification of a contact between arginine-180 of the catabolite gene activator protein (CAP) and base pair 5 of the DNA site in the CAP-DNA complex.
abstract: We have used site-directed mutagenesis to replace amino acid 1 of the recognition alpha-helix of the catabolite gene activator protein (CAP), Arg-180, with glycine and with alanine. Substitution of Arg-180 of CAP eliminated specificity between G.C, A.T, C.G, and T.A at base pair 5 of the DNA half-site. The effect was position-specific: substitution of Arg-180 did not eliminate specificity between G.C, A.T, C.G, and T.A at base pair 7 of the DNA half-site. We conclude, in agreement with the model for the structure of the CAP-DNA complex [Weber, I. & Steitz, T. (1984) Proc. Natl. Acad. Sci. USA 81, 3973-3977; and Ebright, R., Cossart, P., Gicquel-Sanzey, B. & Beckwith, J. (1984) Proc. Natl. Acad. Sci. USA 81, 7274-7278], that Arg-180 of CAP makes a specificity-determining contact with base pair 5 of the DNA half-site in the CAP-DNA complex. The identification of the contact by Arg-180 in this report, in conjunction with the identification of the contact by Glu-181 in a previous report [Ebright, R., Cossart, P., Gicquel-Sanzey, B. & Beckwith, J. (1984) Nature (London) 311, 232-235], provides information sufficient to define the orientation of the helix-turn-helix motif of CAP with respect to DNA in the CAP-DNA complex.
authors.affiliation: Department of Chemistry, Rutgers University, New Brunswick, NJ 08855.
authors.forename: X P
authors.initials: XP
authors.lastname: Zhang
authors.forename: R H
authors.initials: RH
authors.lastname: Ebright
mesh_terms: D000409:Alanine; D001120:Arginine; D001482:Base Composition; D001483:Base Sequence; D001665:Binding Sites; D003090:Coliphages / Q000235:genetics; D002373:Cyclic AMP Receptor Protein / Q000235:genetics* / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics*; D005998:Glycine; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D002373:Cyclic AMP Receptor Protein; D004247:DNA; D001120:Arginine; D000409:Alanine; D005998:Glycine