Solution structure analysis of the conformational changes that occur upon the binding of the protein kinase inhibitor peptide to the catalytic subunit of the cAMP dependent protein kinase

摘要

Fourier transform infrared (FTIR) spectroscopy and small-angle x-ray scattering experiments have been used to examine both the secondary structure content and overall conformation, respectively, of the catalytic subunit of the cAMP-dependent protein kinase and to characterize the structural change that occurs upon binding of the protein kinase inhibitor peptide, PKI(5-22)amide. While the secondary structure of the enzyme is unaltered by the binding of PKI(5-22)amide, a large overall conformational change occurs resulting in a compaction of the enzyme that is characterized by a 2(angstrom) decrease in radius of gyration, Rg, and an 11(angstrom) decrease in the maximum linear dimension, d(sub max). We have modeled the conformational change as a simple rotation of the upper and lower lobes of the kinase by 39(degrees) about a molecular hinge defined by Glyl25, resulting in a closure of the cleft between the two lobes of the kinase. These data are evaluated with respect to recent x-ray crystallographic studies of the cAMP-dependent protein kinase, CDK2 protein kinase, and the MAP kinase ERK2. In addition, the implications that these findings have for the remainder of the protein kinase family are discussed.