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A deletion that removes one repetitive extragenic palindromic sequence downstream of the structural gene of Escherichia coli glutamate dehydrogenase, reduces twofold the half-life of gdhA mRNA.

A 2.3-kb PstI- ClaI chromosomal DNA segment, carrying the complete coding region of the glutamate dehydrogenase (GDH) structural gene from Escherichia coli K-12, has been sequenced. The complete amino acid sequence (447 residues) of the GDH monomer has been deduced, and comparisons are made with reported amino acid sequences of GDH from other organisms.

We have determined the complete nucleotide sequence of a 6.3-kb chromosomal HpaI-EcoRI fragment, that contains the structural genes for both the large and small subunits of the Escherichia coli K-12 glutamate synthase (GOGAT) enzyme, as well as the 5'- and 3'-flanking and intercistronic DNA regions. The Mrs of the two subunits, as deduced from the nucleotide (nt) sequence, were estimated as 166,208 and 52,246. Partial amino acid sequence of the GOGAT enzyme revealed that the large subunit starts with a cysteine residue that is probably generated by a proteolytic cleavage. Northern blotting experiments revealed a transcript of approximately 7300 nt, that at least contains the cistrons for both subunits. A transcriptional start point and a functional promoter were identified in the 5' DNA flanking region of the large subunit gene. The messenger RNA nontranslated leader region has 120 nt and shares identity with the leader regions of E. coli ribosomal operons, in particular around the so-called boxA sequence implicated in antitermination. Other possible regulatory sequences are described.

Deletions of the 3' flanking DNA region of the glutamate dehydrogenase (GDH) structural gene from Escherichia coli K-12, have been produced on a plasmid that carries the complete gdhA gene. Those deletions include part of the repetitive extragenic palindromic (REP) sequences proposed by Stern et al. [Cell 37 (1984) 1015-1026], as a novel and major feature of the bacterial genome. The effect of these deletions on the final GDH level in the cell, has been determined. A broader compilation, analysis and alternative functions of the REP sequences, is also presented.