DNA sequence of a plasmid-encoded dihydrofolate reductase

Galvin Swift, Brian J. McCarthy, Fred Heffron

Research output: Contribution to journalArticlepeer-review

57 Scopus citations


The sequence of the methotrexate-resistant dihydrofolate reductase (DHFR) gene borne by the plasmid R-388 was determined. The gene was subcloned and mapped by an in vitro mutagenesis method involving insertion of synthetic oligonucleotide decamers encoding the BamHI recognition site. Sites of insertion that destroyed the methotrexate resistance fell in two regions separated by 300 bp within a 1.2 kb fragment. One of these regions encodes a 78 amino acid polypeptide homologous to another drug-resistant DHFR. The second region essential for DHFR expression appears to be the promoter of the DHFR gene.

Original languageEnglish (US)
Pages (from-to)441-447
Number of pages7
JournalMGG Molecular & General Genetics
Issue number4
StatePublished - May 1 1981

ASJC Scopus subject areas

  • Genetics


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