title: Photoaffinity labeling of the adenosine cyclic 3',5'-monophosphate receptor protein of Escherichia coli with 8-azidoadenosine 3',5'-monophosphate.
abstract: Photoaffinity labeling of the cAMP receptor protein (CRP) of Escherichia coli with 8-azidoadenosine 3',5'-monophosphate (8-N3cAMP) has been demonstrated. 8-N3cAMP is able to support the binding of (3H)d(I-C)n by CRP, indicating that it is a functional cAMP analogue. Following irradiation at 254 nm, (32P)-8-N3cAMP is photocross-linked to CRP. Photolabeling of CRP by (32P)-8-N3cAMP is inhibited by cAMP but not by 5'AMP. The data indicate that (32P)-8-N3cAMP is covalently incorporated following binding at the cAMP binding site of CRP. The (32P)-8-N3cAMP-CRP digested with chymotrypsin was analyzed by NaDodSO4-polyacrylamide gel electrophoresis. Of the incorporated label, one-third remains associated with the amino-proximal alpha core region of CRP [Eilen, E., Pampeno, C., & Krakow, J.S. (1978) Biochemistry 17, 2469] which contains the cAMP binding domain; the remaining two-thirds of the label associated with the beta region are digested. Limited proteolysis of the (32P)-8-N3cAMP-CRP by chymotrypsin in the presence of NaDodSO4 shows the radioactivity to be distributed between the molecular weight 9500 (amino-proximal) and 13,000 (carboxyl-proximal) fragments produced. These results suggest that a part of the carboxyl-proximal region is folded over and close enough to the cAMP binding site to be cross-linked by the photoactivated (32P)-8-N3cAMP bound at the cAMP binding site.
mesh_terms: D000345:Affinity Labels; D001386:Azides; D001667:Binding, Competitive; D003432:Cross-Linking Reagents; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000528:radiation effects; D004926:Escherichia coli / Q000378:metabolism*; D007700:Kinetics; D008970:Molecular Weight; D011953:Receptors, Cyclic AMP / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D000345:Affinity Labels; D001386:Azides; D003432:Cross-Linking Reagents; D011953:Receptors, Cyclic AMP; C017042:8-azidoadenosine-3',5'-monophosphate; D000242:Cyclic AMP