Open AccessMutant strains of Tetrahymena thermophila defective in thymidine kinase activity: biochemical and genetic characterization.
Author(s) -
K V Cornish,
Ronald E. Pearlman
Publication year - 1982
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.2.8.930
Subject(s) - thymidine kinase , biology , tetrahymena , thymidine , mutant , phosphotransferase , microbiology and biotechnology , biochemistry , kinase , enzyme , nucleoside , in vitro , genetics , gene , virus , herpes simplex virus
Three mutant strains, one conditional, of Tetrahymena thermophila were defective in thymidine phosphorylating activity in vivo and in thymidine kinase activity in vitro. Nucleoside phosphotransferase activity in mutant cell extracts approached wild-type levels, suggesting that thymidine kinase is responsible for most, if not all, thymidine phosphorylation in vivo. Thymidine kinase activity in extracts of the conditional mutant strain was deficient when the cells were grown or assayed or both at the permissive temperature, implying a structural enzyme defect. Analysis of the reaction products from in vitro assays with partially purified enzymes showed that phosphorylation by thymidine kinase and nucleoside phosphotransferase occurred at the 5' position. Genetic analyses showed that the mutant phenotype was recessive and that mutations in each of the three mutant strains did not complement, suggesting allelism.