Hill R T, Parker J R, Goodman H J, Jones D T, Woods D R
Department of Microbiology, University of Cape Town, South Africa.
J Gen Microbiol. 1989 Dec;135(12):3271-9. doi: 10.1099/00221287-135-12-3271.
The nucleotide sequence of a 2777 bp DNA segment containing the Bacteroides fragilis glnA gene was determined. The B. fragilis glnA open reading frame of 2187 bp encoded a glutamine synthetase (GS) subunit of 729 amino acid residues with a calculated Mr of 82,827. The apparent Mr of the GS subunit determined by SDS-PAGE was approximately 75,000. A single mRNA transcription start point was identified upstream of the B. fragilis glnA open reading frame. The B. fragilis GS subunit is approximately 270 and 400 amino acids longer than the GSI and GSII subunits, respectively, of other prokaryotes and eukaryotes. The GSI and GSII holoenzymes are dodecamers and octamers respectively, whereas the GS of B. fragilis is a hexamer. Although GSI and GSII subunits show amino acid similarity in five conserved regions, this similarity is not strongly conserved in the B. fragilis GS. The GS of B. fragilis is not regulated by adenylylation and lacks the adenylylation site. It also lacks the Trp residue associated with the active site in GSI and GSII enzymes from other prokaryotes and eukaryotes.
测定了一段包含脆弱拟杆菌谷氨酰胺合成酶基因（glnA）的2777bp DNA片段的核苷酸序列。脆弱拟杆菌的glnA开放阅读框为2187bp，编码一个由729个氨基酸残基组成的谷氨酰胺合成酶（GS）亚基，计算所得的相对分子质量为82,827。通过SDS-PAGE测定的GS亚基的表观相对分子质量约为75,000。在脆弱拟杆菌glnA开放阅读框上游鉴定出一个单一的mRNA转录起始点。脆弱拟杆菌的GS亚基分别比其他原核生物和真核生物的GSI和GSII亚基长约270和400个氨基酸。GSI和GSII全酶分别是十二聚体和八聚体，而脆弱拟杆菌的GS是六聚体。尽管GSI和GSII亚基在五个保守区域显示出氨基酸相似性，但这种相似性在脆弱拟杆菌的GS中并不高度保守。脆弱拟杆菌的GS不受腺苷酸化调节，并且缺乏腺苷酸化位点。它还缺乏与其他原核生物和真核生物的GSI和GSII酶活性位点相关的色氨酸残基。
