Abstract
We screened cyclin-dependent protein kinase inhibitors from culture media of soil microorganisms by in vitro enzyme assay system using a specific synthetic peptide substrate, CSH103. A selective and very potent inhibitor of CDC2 kinase activity was isolated from the culture medium of Streptomyces sp. LPL931 and identified as toyocamycin (C12H13N5O4, Mr 291.266). To determine whether toyocamycin is able to specifically inhibit cyclin dependent kinase (CDK) family kinase activity, a histone H1 kinase assay was performed with immunoprecipitates of CDC2 or CDK2 using specific antibodies. The result showed that toyocamycin competitively inhibits immunoprecipitated CDC2 kinase activity with a Ki value of 1.55 μM against ATP and an IC50 value of 0.88 μM. This nucleoside antibiotic also inhibited immunoprecipitated CDK2 kinase activity with an IC50 value of about 1 μM, but inhibited less effectively other kinases tested. Furthermore, MTT assay revealed that the agent is able to suppress cell proliferation of Sk-Hep-1 cells at a concentration of 1-10 μM.
Original language | English (US) |
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Pages (from-to) | 679-683 |
Number of pages | 5 |
Journal | Molecules and Cells |
Volume | 6 |
Issue number | 6 |
DOIs | |
State | Published - Dec 31 1996 |
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology