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PubMed · 376528

R plasmid dihydrofolate reductase with subunit structure.

S L Smith·D Stone·P Novak·D P Baccanari·J J Burchall
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Abstract

Dihydrofolate reductase, specified by the type II plasmid of a trimethoprim-resistant Escherichia coli, was purified 40-fold to homogeneity using a combination of gel filtration, DEAE-Sephacel chromatography, and hydrophobic chromatography. The final product shows a single protein band on polyacrylamide gel electrophoresis and has a specific activity of 1.0 unit/mg. The molecular weight of the purified enzyme is 36,000 as determined both by gel filtration and Ferguson analysis of polyacrylamide gel electrophoresis. In contrast, a single polypeptide with a molecular weight of 8,500 was observed on sodium dodecyl sulfate-gel electrophoresis. These experiments suggest that, unlike any bacteria or vertebrate dihydrofolate reductase previously examined, the type II R plasmid reductase is a tetramer composed of four identical subunits. A partial amino acid sequence determination shows no heterogeneity of the subunits and also no clear homology with any reductase sequence previously reported.

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Amino Acid SequenceEscherichia coliMacromolecular SubstancesMolecular WeightPlasmidsTetrahydrofolate DehydrogenaseTransformation, GeneticTrimethoprimJournal Article

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S L Smith, D Stone, P Novak, D P Baccanari, J J Burchall. 1979-07-25. R plasmid dihydrofolate reductase with subunit structure.. https://pubmed.ncbi.nlm.nih.gov/376528/

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