PfkB and pfkC loci of Escherichia coli.
AUTOR(ES)
Vinopal, R T
RESUMO
Mutants lacking Escherichia coli phosphofructokinase (pfkA, 78 min) are suppressed by the unlinked pfkB1 mutation, which restores some enzyme activity (Morrissey and Fraenkel, 1972). We here describe a secondary mutation at pfkB, "PFKB-," which abolishes the suppression as well as the low residual activity of unsuppressed pfkA mutants. pfkB is at about 33 min. with the gene order groD-pps-pheS-pfkB. A positive selection was found that yielded both the pfkB-mutations and a new similar mutation, pfkC-. pfkC is an early marker in Hfr HL16(ca. 50 to 55 min). Some pfkC-, but no pfkB-, mutations were amber. A temperature-sensitive pfkB- was also obtained. Strains carrying pfkB- or pfkC-, but wild type at pfkA, were not markedly affected in growth on sugars. A new search for suppressors such as pfkB1 gave five independent candidates, all of which suppressed both pfkA1 and pfkA2 and occurred in the pfkB region; none occurred at pfkC. Neither the pfkB nor the pfkC loci have assigned functions. It is likely that they are somehow involved in expression of phosphofructokinase activity 2 (Fraenkel, Kotlarz, and Buc, 1973).
