GLC LOCUS OF ESCHERICHIA-COLI - CHARACTERIZATION OF GENES ENCODING THE SUBUNITS OF GLYCOLATE OXIDASE AND THE GLC REGULATOR PROTEIN

The locus glc (min 64.5), associated with the glycolate utilization tr ait in Escherichia coli, is known to contain glcB, encoding malate syn thase G, and the gene(s) needed for glycolate oxidase activity. Subclo ning, sequencing, insertion mutagenesis, and expression studies showed five additional genes: glcC and in the other direction glcD, glcE, gl cF, and glcC followed by glcB. The gene glcC may encode the glc regula tor protein. Consistently a chloramphenicol acetyltransferase insertio n mutation abolished both glycolate oxidase and malate synthase G acti vities. The proteins encoded from glcD and glcE displayed similarity t o several flavoenzymes, the one from glcF was found to be similar to i ron-sulfur proteins, and that from glcG had no significant similarity to any group of proteins. The insertional mutation by a chloramphenico l acetyltransferase cassette in either glcD, glcE, or glcF abolished g lycolate oxidase activity, indicating that presumably these proteins a re subunits of this enzyme. No effect on glycolate metabolism was dete cted by insertional mutation in glcC. Northern (RNA) blot experiments showed constitutive expression of glcC but induced expression for the structural genes and provided no evidence for a single polycistronic t ranscript.