Coudart-Cavalli M P, Sismeiro O, Danchin A
DKFZ, Deutsches Krebs Forschung Zentrum, Heidelberg, Germany.
Biochimie. 1997 Dec;79(12):757-67. doi: 10.1016/s0300-9084(97)86934-9.
Two adenylyl cyclase genes (cyaA and cyaB) from the myxobacterium Stigmatella aurantiaca were cloned by complementation of Escherichia coli mutants defective in the cya gene. cyaA codes for a protein of 424 amino acid residues (AC1), while cyaB encodes a protein of 352 residues (AC2). Both cyclases are sensitive to adenosine: cAMP production was strongly inhibited in E coli cells and cell extracts expressing these genes. AC1 comprises a hydrophobic domain of six transmembrane helices coupled to a cytoplasmic catalytic domain endowed with adenylyl cyclase activity. A 17 amino acid residue sequence, which is a signature of G-protein coupled receptors, as well as of slime mold Dictyostelium discoideum cyclic AMP receptors, was found in the membrane domain. AC2 displays features also indicating that it is a bifunctional enzyme. The domain located upstream from the catalytic adenylyl cyclase domain shows strong similarity to receiver modules of response regulators of two-component bacterial signaling systems. In vitro mutagenesis of conserved aspartate residues in this domain was shown to interfere with cAMP synthesis.
通过对cya基因缺陷的大肠杆菌突变体进行互补，克隆了来自粘细菌橙黄标桩菌的两个腺苷酸环化酶基因（cyaA和cyaB）。cyaA编码一个由424个氨基酸残基组成的蛋白质（AC1），而cyaB编码一个由352个残基组成的蛋白质（AC2）。两种环化酶对腺苷都敏感：在表达这些基因的大肠杆菌细胞和细胞提取物中，cAMP的产生受到强烈抑制。AC1包含一个由六个跨膜螺旋组成的疏水结构域，与一个具有腺苷酸环化酶活性的胞质催化结构域相连。在膜结构域中发现了一个17个氨基酸残基的序列，它是G蛋白偶联受体以及黏菌盘基网柄菌环化AMP受体的特征序列。AC2也显示出其是一种双功能酶的特征。位于催化腺苷酸环化酶结构域上游的结构域与双组分细菌信号系统响应调节因子的受体模块有很强的相似性。该结构域中保守天冬氨酸残基的体外诱变显示会干扰cAMP的合成。
