Hillemann D, Dammann T, Hillemann A, Wohlleben W
Universität Bielefeld, Lehrstuhl für Genetik, Germany.
J Gen Microbiol. 1993 Aug;139(8):1773-83. doi: 10.1099/00221287-139-8-1773.
The 1410 bp DNA region (glnA) encoding glutamine synthetase I (GSI) from Streptomyces viridochromogenes was amplified by PCR, cloned and sequenced. The molecular mass of the deduced GSI protein (469 residues) was determined to be 50 kDa. The DNA region showed 90% nucleotide identity with the Streptomyces coelicolor A3(2) glnA gene, but no significant nucleotide sequence similarity with the glnII (GSII) gene of S. viridochromogenes. The chromosomal glnA and glnII genes of S. viridochromogenes were disrupted by site-specific mutagenesis. Neither glnA nor glnII single mutants required glutamine for growth and both were normal in their sporulation. Measurement of the GS activity in cultures grown with different nitrogen sources revealed that GSI (heat-stable) and GSII (heat-labile) were always expressed together, with GSI as the predominant activity. It could be proposed that GSI, but not GSII is inactivated by adenylylation under conditions of nitrogen excess. GSI and GSII activities are inhibited by amino acids and by nucleotides.
通过聚合酶链反应（PCR）扩增、克隆并测序了来自绿色产色链霉菌的编码谷氨酰胺合成酶I（GSI）的1410 bp DNA区域（glnA）。推导的GSI蛋白（469个残基）的分子量确定为50 kDa。该DNA区域与天蓝色链霉菌A3(2)的glnA基因显示出90%的核苷酸同一性，但与绿色产色链霉菌的glnII（GSII）基因没有明显的核苷酸序列相似性。通过位点特异性诱变破坏了绿色产色链霉菌的染色体glnA和glnII基因。glnA和glnII单突变体在生长时均不需要谷氨酰胺，且两者的孢子形成均正常。对在不同氮源下培养的菌株中的GS活性进行测量，结果表明GSI（热稳定）和GSII（热不稳定）总是一起表达，且以GSI为主要活性。可以推测，在氮过量的条件下，GSI而非GSII会被腺苷酸化失活。GSI和GSII的活性受到氨基酸和核苷酸的抑制。
