Open AccessAmino‐terminal methionine processing of the protein HPr in Streptococcus salivarius grown in continuous culture
Author(s) -
Vadeboncoeur Christian,
Brochu Denis,
Trahan Luc,
Fradette Julie,
Gingras Sébastien
Publication year - 1993
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1993.tb06385.x
Subject(s) - streptococcus salivarius , pep group translocation , phosphoenolpyruvate carboxykinase , galactose , methionine , chemistry , biochemistry , sugar , carbohydrate , biology , food science , amino acid , streptococcus , bacteria , enzyme , genetics
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.