Replacing the general energy-coupling proteins of the phospho-enol-pyruvate: sugar phosphotransferase system of Salmonella typhimurium with fructose-inducible counterparts results in the inability to utilize nonphosphotransferase system sugars.
A Salmonella typhimurium mutant lacking Enzyme I and HPr, general proteins of the phosphoenolpyruvate:sugar phosphotransferase system (PTS), but producing homologues EI(Fructose) and FPr constitutively, did not grow in minimal medium supplemented with non-PTS sugars (melibiose, glycerol, and maltose) in the absence of any trace of Luria-Bertani broth; adding cyclic AMP allowed growth. On melibiose, rapid growth began only when melibiose permease activity had reached a threshold level. Wild-type cultures reached this level within about 2 h, but the mutant only after a 12-14 h lag period, and then only when cyclic AMP had been added to the medium. On a mixture of melibiose and a PTS sugar, permease was undetectable in either the wild type or mutant until the PTS sugar had been exhausted. Permease then appeared, increasing with time, but in the mutant it never reached the threshold allowing rapid growth on melibiose unless cyclic AMP had been added. On rich medium supplemented with melibiose or glycerol, the mutant produced lower (30%) levels of melibiose permease or glycerol kinase compared with the wild type. We propose that poor phosphorylation of the regulatory protein Enzyme IIA(Glucose), leading to constitutive inducer exclusion and catabolite repression in this strain, accounts for these results.
Sutrina
Sarah L
SL
Department of Biological and Chemical Sciences, The University of the West Indies, Cave Hill Campus, Barbados. ssutrina@uwichill.edu.bb
Inniss
Patricia I
PI
Lazarus
Leslie-Ann
LA
Inglis
Lizette
L
Maximilien
Jacqueline
J
D001426:Bacterial Proteins / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D005632:Fructose / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D047908:Intracellular Signaling Peptides and Proteins; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000235:genetics / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000201:enzymology / Q000254:growth & development* / Q000502:physiology*; D013012:Sorbitol / Q000378:metabolism*
D001426:Bacterial Proteins; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C028640:fructose-induced HPr-like protein, bacteria; D005632:Fructose; D013012:Sorbitol; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C030182:phosphocarrier protein HPr