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Nucleotide sequences of glnB and glnA genes from Rhodobacter sphaeroides

Han Tao, Wu Yongqiang, Song Hongyu

Shanghai Institute of Plant Physiology, The Chinese Academy of Sciences. Shanghai 200032

Abstract

Complete nucleotide sequences of the glnA gene (structural gene for glutamine synethase) and glnB gene (structural gene for PIIprotein) from the purple non-sulphur photosynthetic bacterium Rhodobacter sphaeroides were determined. The glnA gene is composed of 1401 nt and is corresponding to 467amino acid residues; the glnB gene is composed of 336 nt, which encode a 112 residue polypeptide. The GC content of the 2707　nt DNA sequence is 65%, which is close to the total GC content of R. sphaeroides. The probability of GCon third position of the codon is 89.1%. Comparison of the deduced amino acid sequences of GS and PII protein from R. sphaeroides with those fromother bacteria separately suggests that the GS protein of R. sphaeroides is more similar to the GS proteins from nitrogen fixation bacteria than that of the enteric bacteria, but the homological parts of PII protein between these kinds of bacteria are very similar. And we found the same sequence 5^AAAGGG3^ upstream the two ORFs of the glnA and glnB genes, which were suspected as the ribosome binding site (RBS). But we have not found any E. coli-like promoter sequence upstream the glnA and glnB genes of the R. sphaeroides. There are some inverted repeated sequencs, these sequences might play a regulatory role in the course of transcription of glnB and glnA gene.

Key words: Rhodobacter sphaeriodes;Glutamine synthetase;GlnA gene;glnB gene;Nitrogen fixation

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Citing This Article：

Han Tao, Wu Yongqiang, Song Hongyu. Nucleotide sequences of glnB and glnA genes from Rhodobacter sphaeroides. Acta Physiol Sin 1997; 49 (2): (in Chinese with English abstract).