GO_REF:0000043

Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping

Source of IEA annotations for oxidoreductase activity, one-carbon metabolic process, response to methotrexate, and response to antibiotic

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods

Source of IEA annotations for DHFR activity and tetrahydrofolate biosynthetic process based on InterPro domains

PMID:4936128

T4 bacteriophage-specific dihydrofolate reductase: purification to homogeneity by affinity chromatography.

First purification and enzymatic characterization of T4 DHFR

"T4 bacteriophage-specific dihydrofolate reductase: purification to homogeneity by affinity chromatography"

PMID:10818362

Overexpression, crystallization and preliminary X-ray crystallographic analysis of dihydrofolate reductase from bacteriophage T4

Crystal structure determination and confirmation of homodimer structure

"Dihydrofolate reductase (DHFR) from bacteriophage T4 is a homodimer consisting of 193-residue subunits"

PMID:6327673

Nucleotide sequence reveals overlap between T4 phage genes encoding dihydrofolate reductase and thymidylate synthase

frd gene encodes 193 amino acid DHFR and overlaps with thymidylate synthase gene

"This fragment contains the structural gene (frd) for dihydrofolate reductase and part of the gene (td) encoding thymidylate synthase...a 579-base-pair open reading frame, encoding a 193-residue polypeptide with a calculated mass of 21,603 Da"

PMID:1560001

Specific associations of T4 bacteriophage proteins with immobilized deoxycytidylate hydroxymethylase

DHFR interacts with deoxycytidylate 5-hydroxymethyltransferase as part of dNTP synthetase complex

"Several of the T4 proteins were identified by two-dimensional gel electrophoresis and radioautography. These include five enzymes involved in DNA precursor biosynthesis, dCMP hydroxymethylase, thymidylate synthase, dihydrofolate reductase, dCTPase-dUTPase, and ribonucleotide reductase"

file:BPT4/frd/frd-deep-research-falcon.md

Deep research summary for T4 phage frd (DHFR)

T4 DHFR catalyzes reduction of dihydrofolate to tetrahydrofolate using NADPH

"T4 DHFR catalyzes the two-electron reduction of dihydrofolate (FH2) to tetrahydrofolate (FH4), using NADPH as the hydride donor"
Phage DHFRs do not confer antibiotic resistance

"phage-encoded DHFRs (found on cryptic plasmids/phages) do not confer trimethoprim resistance despite homology"

file:BPT4/frd/frd-notes.md

Manual deep-review notes for T4 frd

Later immunoblot evidence disputes the older claim that T4 DHFR is a bona fide virion/baseplate structural protein.

"Chen et al. 1995 concluded that T4 thymidylate synthase and DHFR are present only as minor contaminants, less than 0.05 copy per phage, and cannot be bona fide structural proteins."