Streicher S L, Tyler B
Proc Natl Acad Sci U S A. 1981 Jan;78(1):229-33. doi: 10.1073/pnas.78.1.229.
The enzymatic activity of glutamine synthetase [GS; L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2] from the Gram-positive bacterium Streptomyces cattleya is regulated by covalent modification. In whole cells containing high levels of GS the addition of ammonium chloride leads to a rapid decline in GS activity. Crude extracts prepared from such ammonia-shocked cells had very low levels of GS activity as measured by biosynthetic and gamma-glutamyltransferase assays. Incubation of the crude extracts with snake venom phosphodiesterase restored GS activity. In cell extracts, GS was also inactivated by an ATP- and glutamine-dependent reaction. Radioactive labeling studies demonstrated the incorporation of an AmP moiety into GS protein upon modification. Our results suggest a covalent modification of GS in a Gram-positive bacterium. This modification appears to be adenylylation of the GS subunit similar to that found in the Gram-negative bacteria.
革兰氏阳性菌卡特利链霉菌中谷氨酰胺合成酶[GS；L-谷氨酸：氨连接酶（形成ADP），EC 6.3.1.2]的酶活性受共价修饰调节。在含有高水平GS的全细胞中，添加氯化铵会导致GS活性迅速下降。通过生物合成和γ-谷氨酰转移酶测定法测量，从这种氨冲击细胞制备的粗提取物中GS活性水平非常低。将粗提取物与蛇毒磷酸二酯酶一起孵育可恢复GS活性。在细胞提取物中，GS也通过ATP和谷氨酰胺依赖性反应失活。放射性标记研究表明，修饰后GS蛋白中掺入了一个AmP部分。我们的结果表明革兰氏阳性菌中GS存在共价修饰。这种修饰似乎是GS亚基的腺苷酰化，类似于在革兰氏阴性菌中发现的情况。
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