| Popis: |
Recent Escherichia coli genome sequencing efforts in the 76–81.5 min and 92.8–0.1 min regions have revealed three new operons or gene clusters concerned with sugar metabolism, which we designate sga (6 ORFs), sgb (4 ORFs), and sgc (6 ORFs). All of these operons encode proteins homologous to pentose-phosphate-4-epimerases (sga and sgb) or pentose-phosphate-3-epimerases (sgc), indicating that these operons are involved in the metabolism of pentoses or pentitols. sga and sgc (but not sgb) encode also proteins of the bacterial phosphotransferase system (PTS), whereas sga and sgb encode three non-PTS proteins (one of which is the pentose-phosphate-4-epimerase homologue) that are homologous to each other. The two PTS protein homologues in the sga operon are members of (1) the family of mannitol-specific and fructose-specific IIA proteins and (2) the family of lactose-specific and cellobiose-specific IIB proteins. A IIC PTS homologue was not found in the sga operon, but a permease-like protein designate... |
