Weber I T, Takio K, Titani K, Steitz T A
Proc Natl Acad Sci U S A. 1982 Dec;79(24):7679-83. doi: 10.1073/pnas.79.24.7679.
Comparison of the recently determined amino acid sequences of the regulatory subunit of cAMP-dependent protein kinase (RII) from bovine cardiac muscle and the Escherichia coli catabolite gene activator protein (CAP) shows significant homology. This homology extends over most of the amino-terminal domain in CAP and is particularly good for the region of the beta-roll structure. The RII sequence contains two adjacent and internally homologous regions, both of which have high resemblance to the cAMP-binding domain in CAP. This suggests that the protein kinase regulatory subunit contains two cAMP-binding domains in the carboxyl-terminal region, each having a beta-roll structure similar to that in CAP. The cAMP molecule is expected to bind to the RII within a pocket formed by residues from the beta-roll, as is the case with CAP. One cAMP molecule would interact with residues from about 163 to 220, and the other cAMP would interact with amino acids in the stretch 285-350 of the RII protein kinase sequence. As the carboxyl-terminal domain of CAP shows homologies to the DNA-binding domains of other regulatory proteins, the protein appears to be of modular construction: a DNA-binding domain joined to a cAMP-binding domain.
对最近测定的来自牛心肌的环磷酸腺苷（cAMP）依赖性蛋白激酶调节亚基（RII）和大肠杆菌分解代谢基因激活蛋白（CAP）的氨基酸序列进行比较，结果显示出显著的同源性。这种同源性延伸至CAP的大部分氨基末端结构域，对β-折叠结构区域尤为明显。RII序列包含两个相邻且内部同源的区域，这两个区域与CAP中的cAMP结合结构域都有高度相似性。这表明蛋白激酶调节亚基在羧基末端区域含有两个cAMP结合结构域，每个结构域都具有与CAP中类似的β-折叠结构。预计cAMP分子会像在CAP中一样，结合到由β-折叠中的残基形成的口袋内的RII上。一个cAMP分子会与大约163至220位的残基相互作用，另一个cAMP会与RII蛋白激酶序列中285 - 350片段的氨基酸相互作用。由于CAP的羧基末端结构域与其他调节蛋白的DNA结合结构域显示出同源性，该蛋白似乎具有模块化结构：一个DNA结合结构域连接到一个cAMP结合结构域。
