Atkinson R A, Saudek V, Huggins J P, Pelton J T
Marion Merrell Dow Research Institute, Strasbourg, France.
Biochemistry. 1991 Oct 1;30(39):9387-95. doi: 10.1021/bi00103a001.
Cyclic GMP dependent protein kinase exists as a dimer in its native form. A peptide corresponding to the dimerization domain in the N-terminal segment has been characterized by circular dichroism, ultracentrifugation, and 1H NMR spectroscopy. The peptide (G-kinase1-39 amide) is shown to be dimeric in solution. Determination of the molecular weight of the species in solution from the sedimentation coefficient and diffusion coefficient yields a value more than twice that of the monomeric species. Circular dichroism studies show G-kinase1-39 amide to be largely helical in aqueous solution and stable over a wide range of pH and temperature. The conformational stability is found to be concentration dependent, the peptide having a melting temperature of 75 degrees C (at 20 microM and pH 4.0). The assignment of the 1H NMR spectrum and analysis of the patterns of nuclear Overhauser enhancements confirm the helical nature of the conformation. Distance geometry calculations result in a well-defined helical structure containing a kink near Ser 26. The dimerization of G-kinase is most likely to occur through the hydrophobic interaction of leucine and isoleucine side chains located on one face of a helical structure with supporting electrostatic interactions between flanking side chains. The dimerization domain of G-kinase is clearly analogous to the "leucine zipper" motifs found in a number of DNA transcriptional activators.
环磷酸鸟苷依赖性蛋白激酶以二聚体形式天然存在。一个与N端片段中二聚化结构域相对应的肽段已通过圆二色性、超速离心和1H核磁共振光谱进行了表征。该肽段（G激酶1 - 39酰胺）在溶液中呈二聚体形式。根据沉降系数和扩散系数测定溶液中该物质的分子量，所得值是单体物质分子量的两倍多。圆二色性研究表明，G激酶1 - 39酰胺在水溶液中主要呈螺旋结构，在较宽的pH和温度范围内稳定。发现其构象稳定性与浓度有关，该肽段在20微摩尔浓度和pH 4.0时的解链温度为75摄氏度。1H核磁共振谱的归属以及核Overhauser增强模式的分析证实了该构象的螺旋性质。距离几何计算得出一个明确的螺旋结构，在Ser 26附近有一个扭结。G激酶的二聚化最有可能通过位于螺旋结构一侧的亮氨酸和异亮氨酸侧链的疏水相互作用以及侧翼侧链之间的支持性静电相互作用而发生。G激酶的二聚化结构域明显类似于在许多DNA转录激活因子中发现的“亮氨酸拉链”基序。
