title: Sites of allosteric shift in the structure of the cyclic AMP receptor protein.
abstract: We have characterized crp mutations in E. coli that allow CRP to function without cAMP. crp* mutants carrying a deletion of the gene encoding adenylate cyclase (cya) show significant lac expression. Cyclic GMP, normally an ineffective activator of CRP+, can stimulate these mutant CRP*s to permit greater lac expression in vivo. Cyclic AMP binding to the amino-terminal domain of CRP+ induces an allosteric transition that changes the DNA-binding property of the carboxy domain. The CRP* phenotype is caused by substitution of amino acids with bulkier side chains in the D alpha-helix of the protein's carboxy domain, near the hinge connecting the two domains. These results are consistent with a model in which the mutant CRP*s assume, in part, a conformation normally evoked only by cAMP binding: one in which the relative orientation of the C, D, and F alpha-helices is altered. We define precisely the amino acids of these alpha-helices that interact to cause the allosteric shift.
authors.forename: S
authors.initials: S
authors.lastname: Garges
authors.forename: S
authors.initials: S
authors.lastname: Adhya
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology*; D006152:Cyclic GMP / Q000494:pharmacology; D004926:Escherichia coli / Q000032:analysis; D005796:Genes; D009154:Mutation; D010641:Phenotype; D011487:Protein Conformation / Q000187:drug effects; D011953:Receptors, Cyclic AMP / Q000235:genetics / Q000378:metabolism
chemical_list: D011953:Receptors, Cyclic AMP; D000242:Cyclic AMP; D006152:Cyclic GMP