Open AccessCharacterization of the gene for the chromosomal dihydrofolate reductase (DHFR) of Staphylococcus epidermidis ATCC 14990: the origin of the trimethoprim-resistant S1 DHFR from Staphylococcus aureus?
Author(s) -
Glenn E. Dale,
Clemens Broger,
P. G. Hartman,
Hanno Langen,
Malcolm G. P. Page,
Rudolf L. Then,
Dietrich Stüber
Publication year - 1995
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.177.11.2965-2970.1995
Subject(s) - biology , dihydrofolate reductase , gene , plasmid , operon , staphylococcus epidermidis , trimethoprim , microbiology and biotechnology , open reading frame , escherichia coli , peptide sequence , staphylococcus aureus , genetics , bacteria , antibiotics
The gene for the chromosomally encoded dihydrofolate reductase (DHFR) of Staphylococcus epidermidis ATCC 14990 has been cloned and characterized. The structural gene encodes a polypeptide of 161 amino acid residues with a calculated molecular weight of 18,417. This trimethoprim-sensitive (Tmps) DHFR, SeDHFR, differs in only three amino acids (Val-31-->Ile, Gly-43-->Ala, and Phe-98-->Tyr) from the trimethoprim-resistant (Tmpr) S1 DHFR encoded by transposon Tn4003. Since in addition the S. epidermidis gene also forms part of an operon with thyE and open reading frame 140 as in Tn4003, the chromosomally located gene encoding the Tmps SeDHFR is likely to be the molecular origin of the plasmid-located gene encoding the Tmpr S1 DHFR. Site-directed mutagenesis and kinetic analysis of the purified enzymes suggest that a single Phe-->Tyr change at position 98 is the major determinant of trimethoprim resistance.