期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2003
卷号：100
期号：5
页码：2380-2385
DOI：10.1073/pnas.0534892100
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：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}1-52PKG-I{beta}). On saturation with cGMP, the radius of gyration of {Delta}1-52PKG-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}1-52PKG-I{beta} indicates that elongation of {Delta}1-52PKG-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}1-52PKG-I{beta}. We also predict that there is little or no cooperativity in cGMP binding to the two sites of {Delta}1-52PKG-I{beta} under the conditions used here. Results obtained by using the {Delta}1-52PKG-I{beta} monomer indicate that a previously observed elongation of PKG-I 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.
