TY - JOUR
T1 - Purification and characterization of dihydrofolate reductase from wild-type and trimethoprim-resistant Mycobacterium smegmatis
AU - Sirawaraporn, Worachart
AU - Sirawaraporn, Rachada
AU - Chanpongsri, Atid
AU - Jacobs, William R.
AU - Santi, Daniel V.
N1 - Funding Information:
We thank Dr. K. M. Ivanetich for her reading and helpful suggestions during the preparation of this manuscript, and Ralph Reid for protein sequencing and data analysis. This work was supported by grants from the UNDPlWorld Bank/WHO Special Programme for Research and Training, a GND award from the Rockefeller Foundation, and USPHS A119358. W.S. is a recipient of a Frohlich Research Fellowship.
PY - 1991/2
Y1 - 1991/2
N2 - Dihydrofolate reductase (DHFR) from extracts of Mycobacterium smegmatis strain mc26 and trimethoprim-resistant mutant mc226 was purified to homogeneity. In crude extracts, the specific activity of the enzyme from the trimethoprim resistant strain was comparable to that from the sensitive strain. The DHFR from both sources was purified using affinity chromatography on MTX-Sepharose followed by Mono Q FPLC. The enzyme has an apparent molecular mass of 23 kDa from gel filtration on Sephadex G-100 and from SDS-PAGE. Amino terminal sequence analysis showed homology with DHFRs from a subset of other gram-positive organisms. The purified enzyme from the trimethoprim-sensitive organism exhibited Km values for H2folate and NADPH of 0.68 ± 0.2 μM and 21 ± 4 μM, respectively. The Km values for H2folate and NADPH for the enzyme from the drug-resistant organism were 1.8 ± 0.4 μM and 5.3 ± 1.5 μM, respectively. A Kcat of 4.5 sec-1 was determined for the DHFR from both sources. The enzyme from both sources was competitively inhibited by pyrimethamine and trimethoprim. The Ki value of trimethoprim, for the enzyme from the drug-resistant organism was about six-fold higher than for the enzyme from drug-sensitive strain. Our data suggest that mutation of DHFR contributes to trimethoprim resistance in the mc226 strain of M. smegmatis.
AB - Dihydrofolate reductase (DHFR) from extracts of Mycobacterium smegmatis strain mc26 and trimethoprim-resistant mutant mc226 was purified to homogeneity. In crude extracts, the specific activity of the enzyme from the trimethoprim resistant strain was comparable to that from the sensitive strain. The DHFR from both sources was purified using affinity chromatography on MTX-Sepharose followed by Mono Q FPLC. The enzyme has an apparent molecular mass of 23 kDa from gel filtration on Sephadex G-100 and from SDS-PAGE. Amino terminal sequence analysis showed homology with DHFRs from a subset of other gram-positive organisms. The purified enzyme from the trimethoprim-sensitive organism exhibited Km values for H2folate and NADPH of 0.68 ± 0.2 μM and 21 ± 4 μM, respectively. The Km values for H2folate and NADPH for the enzyme from the drug-resistant organism were 1.8 ± 0.4 μM and 5.3 ± 1.5 μM, respectively. A Kcat of 4.5 sec-1 was determined for the DHFR from both sources. The enzyme from both sources was competitively inhibited by pyrimethamine and trimethoprim. The Ki value of trimethoprim, for the enzyme from the drug-resistant organism was about six-fold higher than for the enzyme from drug-sensitive strain. Our data suggest that mutation of DHFR contributes to trimethoprim resistance in the mc226 strain of M. smegmatis.
KW - Dihydrofolate reductase
KW - Mutation
KW - Mycobacterium smegmatis
KW - Trimethoprim
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U2 - 10.1016/0014-4894(91)90136-K
DO - 10.1016/0014-4894(91)90136-K
M3 - Article
C2 - 2009922
AN - SCOPUS:0026113224
SN - 0014-4894
VL - 72
SP - 184
EP - 190
JO - Experimental Parasitology
JF - Experimental Parasitology
IS - 2
ER -
