期刊
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
卷 19, 期 5, 页码 -出版社
MDPI
DOI: 10.3390/ijms19051393
关键词
thymidylate synthase (TYMS); monomer; dimer; octamer; overexpression and purification
资金
- National Natural Science Foundation of China [81502622]
- Natural Science Foundation of Liaoning Province [201602239]
- National Natural Science Foundation of China (NSFC) [31471328, 81622040]
Thymidylate synthase (TYMS) is an essential enzyme for the de novo synthesis of deoxythymidine monophosphate (dTMP) and has been a primary target for cancer chemotherapy. Although the physical structure of TYMS and the molecular mechanisms of TYMS catalyzing the conversion of deoxyuridine monophosphate (dUMP) to dTMP have been the subject of thorough studies, its oligomeric structure remains unclear. Here, we show that human TYMS not only exists in dimer form but also as an octamer by intermolecular Cys43-disulfide formation. We optimized the expression conditions of recombinant human TYMS using the Escherichia coli system. Using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), we have shown that purified TYMS has catalytic activity for producing dTMP. In the absence of reductant beta-mercaptoethanol, SDS-PAGE and size exclusion chromatography (SEC) showed that the size of the TYMS protein is about 35 kDa, 70 kDa, and 280 kDa. When the Cys43 was mutated to Gly, the band of similar to 280 kDa and the peak of the octamer disappeared. Therefore, TYMS was determined to form an octamer, depending on the presence of Cys43-disulfide. By measuring steady-state parameters for the monomer, dimer, and octamer, we found the k(cat) of the octamer was increased slightly more than the monomer. On the basis of these findings, we suggest that the octamer in the active state might have a potential influence on the design of new drug targets.
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