Progressive cyclic nucleotide-induced conformational changes in the cGMP-dependent protein kinase studied by small angle X-ray scattering in solution.
Small angle scattering data from bovine lung type Ialpha cGMP-dependent protein kinase (PKG) in the absence of cGMP show the protein to have a highly asymmetric structure with a radius of gyration (Rg) of 45 A and a maximum linear dimension (dmax) of 165 A. The addition of cGMP induces a marked conformational change in PKG. The Rg and dmax increase 25-30%, and the protein's mass moves further away from the center of mass; this results in an even more asymmetric structure. Fourier transform infrared spectroscopy data suggest that the conformational change induced by cGMP binding is primarily due to a topographical movement of the structural domains of PKG rather than to secondary structural changes within one or more of the individual domains. Each monomer of the dimeric PKG contains one high and one low affinity cGMP-binding site. A prominent increase in the asymmetry of PKG occurs with binding to high affinity cGMP-binding sites alone, but the full domain movements require the binding to both sets of sites. These conformational changes occurring in PKG with the progressive binding of cGMP to both sets of cGMP-binding sites correlate with past data, which have indicated that cGMP binding to both sets of sites is required for the full activation of the enzyme. These results provide the first quantitative measurement of the overall PKG structure, as well as an assessment of the structural events that accompany the activation of a protein kinase upon binding a small molecular weight ligand.
Zhao
J
J
Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Trewhella
J
J
Corbin
J
J
Francis
S
S
Mitchell
R
R
Brushia
R
R
Walsh
D
D
D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D006152:Cyclic GMP / Q000378:metabolism*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D012542:Scattering, Radiation; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP