Rephaeli A W, Saier M H
J Bacteriol. 1976 Jul;127(1):120-7. doi: 10.1128/jb.127.1.120-127.1976.
Wild-type Salmonella typhimurium could not grow with exogenous cyclic adenosine 3',5'-monophosphate (AMP) as the sole source of phosphate, but mutants capable of cyclic AMP utilization could be isolated provided the parental strain contained a functional cyclic AMP phosphodiesterase.All cyclic AMP-utilizing mutants had the growth and fermentation properties of cyclic AMP receptor protein (crp) mutants, and some lacked cyclic AMP binding activity in vitro. The genetic defect in each such mutant was due to a single point mutation, which was co-transducible with cysG. crp mutants isolated by alternative procedures also exhibited the capacity to utilize cyclic AMP. crp mutants synthesized cyclic AMP at increased rates and contained enhanced cellular cyclic AMP levels relative to the parental strains, regardless of whether or not cyclic AMP phosphodiesterase was active. Moreover, adenylate cyclase activity in vivo was less sensitive to regulation by glucose, possibly because the enzyme II complexes of the phosphotransferase system, responsible for glucose transport and phosphorylation, could not be induced to maximal levels. This possibility was strengthened by the observation that enzyme II activity (measured both in vitro by sugar phosphorylation and in vivo by sugar transport and chemotaxis) was inducible in the parental strain but not in crp mutants. The results suggest that the cyclic AMP receptor protein regulates cyclic AMP metabolism as well as catabolic enzyme synthesis.
野生型鼠伤寒沙门氏菌不能以外源环腺苷酸 3',5'-单磷酸（cAMP）作为唯一磷源生长，但只要亲本菌株含有功能性环腺苷酸磷酸二酯酶，就能分离出能够利用环腺苷酸的突变体。所有利用环腺苷酸的突变体都具有环腺苷酸受体蛋白（crp）突变体的生长和发酵特性，并且一些突变体在体外缺乏环腺苷酸结合活性。每个此类突变体的遗传缺陷都归因于单个点突变，该突变与 cysG 共转导。通过其他方法分离的 crp 突变体也表现出利用环腺苷酸的能力。相对于亲本菌株，crp 突变体以更高的速率合成环腺苷酸并且细胞内环腺苷酸水平升高，无论环腺苷酸磷酸二酯酶是否有活性。此外，体内腺苷酸环化酶活性对葡萄糖调节的敏感性较低，这可能是因为负责葡萄糖转运和磷酸化的磷酸转移酶系统的酶 II 复合物不能被诱导到最大水平。亲本菌株中酶 II 活性（通过体外糖磷酸化和体内糖转运及趋化性测量）是可诱导的，而 crp 突变体中则不然，这一观察结果强化了这种可能性。结果表明，环腺苷酸受体蛋白调节环腺苷酸代谢以及分解代谢酶的合成。
