%0 Journal Article %A Green, Stephen M. %A Malik, Tahir %A Giles, Ian G. %A Drabble, William T. %T The purB gene of Escherichia coli K-12 is located in an operon %D 1996 %J Microbiology, %V 142 %N 11 %P 3219-3230 %@ 1465-2080 %R https://doi.org/10.1099/13500872-142-11-3219 %K internal promoter %K Escherichia coli %K succinyl-AMP lyase %K phoP gene %K purB gene %I Microbiology Society, %X The structural gene (purB) for succinyl-AMP (S-AMP) lyase and three additional ORFs are on the same DNA strand of the chromosome of Escherichia coli. Cassette mutagenesis and primer extension mapping demonstrated that purB is co-transcribed with an upstream gene (ORF23, or ycfC) encoding a 22·9 kDa membrane-associated protein of non-essential, but unknown, function unrelated to purine biosynthesis. The purB operon lies between phoP and an ORF expressing an essential function which may correspond to asuE (trmU). S-AMP lyase was purified to near homogeneity. The purified enzyme is a homotetramer of 50 kDa subunits, has a K m for S-AMP of 3·7 μM and a pH optimum of 7·4–7·6. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/13500872-142-11-3219