Methotrexate(MTX)-resistant human promyelocytic-leukaemia cells (HL-60) derived from MTX-sensitive cells have a 20-fold increase in dihydrofolate reductase (DHFR) activity as compared with the sensitive cells. This increase is not associated with a concomitant increase in DHFR protein as determined by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and by immunological methods using ...

Mass spectrometry technologies for measurement of cellular metabolism are opening new avenues to explore drug activity. Trimethoprim is an antibiotic that inhibits bacterial dihydrofolate reductase (DHFR). Kinetic flux profiling with (15)N-labeled ammonia in Escherichia coli reveals that trimethoprim leads to blockade not only of DHFR but also of another critical enzyme of folate metabolism: fo...

Using cloned DNA complementary to mouse dihydrofolate reductase (DHFR) mRNA, the organization of the hamster DHFR gene has been determined in two baby hamster kidney (BHK) cell lines, A5 and B1. A5 cells are highly methotrexate-resistant, containing 200-fold more copies of the DHFR gene than do the parental B1 cells. The DHFR gene has the same organization in A5 and B1 cells, suggesting that it...

We characterized a highly purified preparation of the chromosomally encoded dihydrofolate reductase (DHFR) from a trimethoprim-susceptible (Tmp8; strain MAP) and two trimethoprim-resistant (TmpR) strains (MAP/47 and MAP/42) of Haemophilus influenzae. The enzymes were purified between 650- and 3000-fold by gel-filtration and dye-ligand chromatography. The apparent molecular mass of the three pro...

Brain tumors are a heterogeneous group of benign and malignant arising from the brain parenchyma its surrounding structures, with in general poor clinical outcome due to high recurrence. One underlying causes for this somber prognostic is presence tumor initiating cells (BTIC) endowed self-renewal potential, multi-lineage differentiation resistance treatment. promising therapeutic avenue target...

Dihydrofolate reductase (DHFR) catalyzes the reduction of dihydrofolate to tetrahydrofolate (THF). THF is needed for the action of folate-dependent enzymes and is thus essential for DNA synthesis and methylation. The importance of this reaction is demonstrated by the effectiveness of antifolate medications used to treat cancer by inhibiting DHFR, thereby depleting THF and slowing DNA synthesis ...

Dihydrofolate reductase (DHFR) is the target of trimethoprim (TMP), which has been widely used in combination with sulfa drugs for treatment and prophylaxis of Pneumocystis carinii pneumonia. While the rat-derived P. carinii DHFR has been well characterized, kinetic studies of human-derived P. carinii DHFR, which differs from rat-derived P. carinii DHFR by 38% in amino acid sequence, have not b...

DHFR (dihydrofolate reductase) catalyses the metabolically important reduction of 7,8-dihydrofolate by NADPH. DHFR from the hyperthermophilic bacterium Thermotoga maritima (TmDHFR), which shares similarity with DHFR from Escherichia coli, has previously been characterized structurally. Its tertiary structure is similar to that of DHFR from E. coli but it is the only DHFR characterized so far th...

R67 dihydrofolate reductase (DHFR), encoded by an R plasmid, provides resistance to the antibacterial drug trimethoprim. This enzyme does not exhibit any structural or sequence homologies with chromosomal DHFR. A recent crystal structure of tetrameric R67 DHFR (D. Matthews, X. Nguyen-huu, and N. Narayana, personal communication) shows a single pore traversing the length of the molecule. Numerou...

Dihydrofolate reductase fusion proteins have been widely used to study conformational properties of polypeptides translocated across membranes. We have studied the import of dihydrofolate reductase fusion proteins into glycosomes and mitochondria of Trypanosoma brucei. As signal sequences we used the last 22 carboxy-terminal amino acids of glycosomal phosphoglycerate kinase for glycosomes, and ...