Tremblay Pier-Luc, Drepper Thomas, Masepohl Bernd, Hallenbeck Patrick C
Département de Microbiologie et Immunologie, Université de Montréal, CP 6128, Succursale Centre-ville, Montréal, Québec, Canada.
J Bacteriol. 2007 Aug;189(16):5850-9. doi: 10.1128/JB.00680-07. Epub 2007 Jun 22.
Both Rhodobacter capsulatus PII homologs GlnB and GlnK were found to be necessary for the proper regulation of nitrogenase activity and modification in response to an ammonium shock. As previously reported for several other bacteria, ammonium addition triggered the AmtB-dependent association of GlnK with the R. capsulatus membrane. Native polyacrylamide gel electrophoresis analysis indicates that the modification/demodification of one PII homolog is aberrant in the absence of the other. In a glnK mutant, more GlnB was found to be membrane associated under these conditions. In a glnB mutant, GlnK fails to be significantly sequestered by AmtB, even though it appears to be fully deuridylylated. Additionally, the ammonium-induced enhanced sequestration by AmtB of the unmodifiable GlnK variant GlnK-Y51F follows the wild-type GlnK pattern with a high level in the cytoplasm without the addition of ammonium and an increased level in the membrane fraction after ammonium treatment. These results suggest that factors other than PII modification are driving its association with AmtB in the membrane in R. capsulatus.
人们发现，荚膜红细菌（Rhodobacter capsulatus）的两个PII同源蛋白GlnB和GlnK对于固氮酶活性的适当调节以及响应铵冲击的修饰是必需的。正如之前对其他几种细菌的报道，添加铵会触发GlnK与荚膜红细菌膜的依赖于AmtB的结合。天然聚丙烯酰胺凝胶电泳分析表明，在缺少另一个PII同源蛋白的情况下，其中一个PII同源蛋白的修饰/去修饰是异常的。在glnK突变体中，在这些条件下发现更多的GlnB与膜相关。在glnB突变体中，尽管GlnK似乎完全去尿苷酸化，但它不能被AmtB显著隔离。此外，铵诱导的不可修饰的GlnK变体GlnK-Y51F被AmtB增强隔离，其遵循野生型GlnK模式，即在不添加铵的情况下细胞质中水平较高，铵处理后膜部分水平增加。这些结果表明，除了PII修饰之外，其他因素也在驱动荚膜红细菌中PII与膜中AmtB的结合。
