title: Daucus carota cells contain a dihydrofolate reductase: thymidylate synthase bifunctional polypeptide.
abstract: Dihydrofolate reductase (DHFR) and thymidylate synthase (TS) activities from cell suspension cultures of Daucus carota were shown to copurify on (NH4)2SO4 fractionation, DEAE Sephadex and methotrexate-Sepharose affinity chromatography and to share approximately the same Mr(183 kDa and 185 kDa respectively) as judged by gel filtration on Sephacryl S-200.The copurified protein migrated as a single band on polyacrylamide gel electrophoresis under denaturing conditions.Both activities could be eluted from the same position of the native gel.Moreover, methotrexate-resistant cell lines which overproduce DHFR revealed to have a parallel higher level of TS. It is therefore proposed and discussed that in carrot, similarly to protozoa, TS and DHFR are present on a single bifunctional polypeptide of 58 kDa.
authors.affiliation: Dipartimento di Genetica e Microbiologia "A. Buzzati Traverso", Sezione di Microbiologia e Fisiologia Vegetale, Università di Pavia, Via S. Epifanio 14, 27100, Pavia, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Cella
authors.forename: E
authors.initials: E
authors.lastname: Nielsen
authors.forename: B
authors.initials: B
authors.lastname: Parisi