A defined subset of adenylyl cyclases is regulated by bicarbonate ion
A defined subset of adenylyl cyclases is regulated by bicarbonate ion
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DOI：
10.1074/jbc.m303025200
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发表时间：
2003-09-12
影响因子：
4.8
通讯作者：
Kanacher, T
中科院分区：
文献类型：
--
作者：
Cann, MJ;Hammer, A;Kanacher, T
生物体检测和响应无机碳波动的分子基础尚不清楚。蓝藻鱼腥藻PCC 7120的cyaB 1基因编码具有C-末端III类腺苷酸环化酶催化剂的多结构域蛋白，该催化剂被碳酸氢根离子特异性刺激（EC 50 9.6 mM）。Bicarboxylic acid降低底物亲和力，但增加反应速度。活性位点（Lys-646）中的点突变使活性降低95%，并且对碳酸氢盐活化是难治的。我们建议，赖氨酸-646具体协调碳酸氢盐在活性位点结合天冬氨酸苏氨酸多态性（Thr-721）保守的III类腺苷酸环化酶从不同的真核生物和原核生物。使用重组蛋白，我们证明，腺苷酸环化酶，含有活性位点苏氨酸（cyaB的金黄色柱头菌和Rv 1319 c的结核分枝杆菌）是碳酸氢盐响应，而腺苷酸环化酶与相应的天冬氨酸（Rv 1264的分枝杆菌）是碳酸氢盐不敏感。因此，大量的III类腺苷酸环化酶可以被碳酸氢盐激活。这代表了一种新的机制，不同的生物体可以检测碳酸氢根离子。
The molecular basis by which organisms detect and respond to fluctuations in inorganic carbon is not known. The cyaB1 gene of the cyanobacterium Anabaena sp. PCC7120 codes for a multidomain protein with a C-terminal class III adenylyl cyclase catalyst that was specifically stimulated by bicarbonate ion (EC50 9.6 mM). Bicarbonate lowered substrate affinity but increased reaction velocity. A point mutation in the active site (Lys-646) reduced activity by 95% and was refractory to bicarbonate activation. We propose that Lys-646 specifically coordinates bicarbonate in the active site in conjunction with an aspartate to threonine polymorphism (Thr-721) conserved in class III adenylyl cyclases from diverse eukaryotes and prokaryotes. Using recombinant proteins we demonstrated that adenylyl cyclases that contain the active site threonine (cyaB of Stigmatella aurantiaca and Rv1319c of Mycobacterium tuberculosis) are bicarbonate-responsive, whereas adenylyl cyclases with a corresponding aspartate (Rv1264 of Mycobacterium) are bicarbonate-insensitive. Large numbers of class III adenylyl cyclases may therefore be activated by bicarbonate. This represents a novel mechanism by which diverse organisms can detect bicarbonate ion.