Amino-terminal methionine processing of the protein HPr in Streptococcus salivarius grown in continuous culture.
HPr is a protein of the phosphoenolpyruvate:sugar phosphotransferase system (PTS). Streptococci possess two forms of HPr which differ by the presence or the absence of the N-terminal methionine (Met). These forms are called HPr-1 (without Met) and HPr-2 (with Met). In order to determine whether the ratio of these two forms varies with growth conditions, we measured the amount of HPr-1 and HPr-2 present in Streptococcus salivarius grown in continuous culture at pH 7.5. The results indicated that the HPr-1/HPr-2 ratio: 1) was not related to the cellular amount of total HPr; 2) was highest (10.2 +/- 3.5) under glucose (a PTS sugar) limitation (10 mM) and low dilution rate (D = 0.1 h-1; g = 6.9 h); 3) was decreased 2.4- to 5.7-fold when the amount of glucose and/or D was increased; 4) was not influenced by D when cells were cultured on galactose (a non-PTS sugar) but was two-fold higher under conditions of galactose excess (200 mM). We suggest that the cleavage of the N-terminal HPr Met is not a stochastic phenomenon but is dictated by growth conditions.
Vadeboncoeur
C
C
Department of Biochemistry (Sciences) and Faculty of Dental Medicine, Université Laval, Québec, Canada.
Brochu
D
D
Trahan
L
L
Fradette
J
J
Gingras
S
S
D000626:Aminopeptidases / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D063208:Methionyl Aminopeptidases; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D013291:Streptococcus / Q000254:growth & development / Q000378:metabolism*
D001426:Bacterial Proteins; D008715:Methionine; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C030182:phosphocarrier protein HPr; D000626:Aminopeptidases; D063208:Methionyl Aminopeptidases