title: Mechanisms associated with cGMP binding and activation of cGMP-dependent protein kinase.
abstract: Using small-angle x-ray scattering, we have observed the cGMP-induced elongation of an active, cGMP-dependent, monomeric deletion mutant of cGMP-dependent protein kinase (Delta(1-52)PKG-I beta). On saturation with cGMP, the radius of gyration of Delta(1-52)PKG-I beta increases from 29.4 +/- 0.1 A to 40.1 +/- 0.7 A, and the maximum linear dimension increases from 90 A +/- 10% to 130 A +/- 10%. The elongation is due to a change in the interaction between structured regulatory (R) and catalytic (C) domains. A model of cGMP binding to Delta(1-52)PKG-I beta indicates that elongation of Delta(1-52)PKG-I beta requires binding of cGMP to the low-affinity binding site of the R domain. A comparison with cAMP-dependent protein kinase suggests that both elongation and activation require cGMP binding to both sites; cGMP binding to the low-affinity site therefore seems to be a necessary, but not sufficient, condition for both elongation and activation of Delta(1-52)PKG-I beta. We also predict that there is little or no cooperativity in cGMP binding to the two sites of Delta(1-52)PKG-I beta under the conditions used here. Results obtained by using the Delta(1-52)PKG-I beta monomer indicate that a previously observed elongation of PKG-I alpha is consistent with a pure change in the interaction between the R domain and the C domain, without alteration of the dimerization interaction. This study has revealed important features of molecular mechanisms in the biochemical network describing PKG-I beta activation by cGMP, yielding new insight into ligand activation of cyclic nucleotide-dependent protein kinases, a class of regulatory proteins that is key to many cellular processes.
authors.affiliation: Computer and Computational Sciences and Bioscience Divisions, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. mewall@lanl.gov
authors.forename: Michael E
authors.initials: ME
authors.lastname: Wall
authors.forename: Sharron H
authors.initials: SH
authors.lastname: Francis
authors.forename: Jackie D
authors.initials: JD
authors.lastname: Corbin
authors.forename: Kennard
authors.initials: K
authors.lastname: Grimes
authors.forename: Robyn
authors.initials: R
authors.lastname: Richie-Jannetta
authors.forename: Jun
authors.initials: J
authors.lastname: Kotera
authors.forename: Brian A
authors.initials: BA
authors.lastname: Macdonald
authors.forename: Rowena R
authors.initials: RR
authors.lastname: Gibson
authors.forename: Jill
authors.initials: J
authors.lastname: Trewhella
mesh_terms: D001665:Binding Sites; D055592:Biophysical Phenomena; D001703:Biophysics; D006152:Cyclic GMP / Q000378:metabolism*; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases / Q000737:chemistry* / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D019281:Dimerization; D004789:Enzyme Activation; D006801:Humans; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012542:Scattering, Radiation; D014965:X-Rays
chemical_list: D018076:DNA, Complementary; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases; C569718:PRKG1 protein, human; D006152:Cyclic GMP