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首页> 外文期刊>Molecular and Cellular Biology >DPH5, a methyltransferase gene required for diphthamide biosynthesis in Saccharomyces cerevisiae.
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DPH5, a methyltransferase gene required for diphthamide biosynthesis in Saccharomyces cerevisiae.

机译：DPH5是酿酒酵母中双硫胺生物合成所需的甲基转移酶基因。

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A mutant of Saccharomyces cerevisiae defective in the S-adenosylmethionine (AdoMet)-dependent methyltransferase step of diphthamide biosynthesis was selected by intracellular expression of the F2 fragment of diphtheria toxin (DT) and shown to belong to complementation group DPH5. The DPH5 gene was cloned, sequenced, and found to encode a 300-residue protein with sequence similarity to bacterial AdoMet:uroporphyrinogen III methyltransferases, enzymes involved in cobalamin (vitamin B12) biosynthesis. Both DPH5 and AdoMet:uroporphyrinogen III methyltransferases lack sequence motifs commonly found in other methyltransferases and may represent a new family of AdoMet:methyltransferases. The DPH5 protein was produced in Escherichia coli and shown to be active in methylation of elongation factor 2 partially purified from the dph5 mutant. A null mutation of the chromosomal DPH5 gene did not affect cell viability, in agreement with other studies indicating that diphthamide is not required for cell survival. The dph5 null mutant survived expression of three enzymically attenuated DT fragments but was killed by expression of fully active DT fragment A. Consistent with these results, elongation factor 2 from the dph5 null mutant was found to have weak ADP-ribosyl acceptor activity, which was detectable only in the presence of high concentrations of fragment A.
机译：通过白喉毒素（DT）的F2片段的细胞内表达选择了在白喉酰胺生物合成的S-腺苷甲硫氨酸（AdoMet）依赖性甲基转移酶步骤中有缺陷的酿酒酵母突变体，该突变体属于互补组DPH5。将DPH5基因克隆，测序并发现其编码300个残基的蛋白质，其序列与细菌AdoMet：尿卟啉原III甲基转移酶（参与钴胺素（维生素B12）生物合成的酶）具有相似性。 DPH5和AdoMet：尿卟啉原III甲基转移酶均缺乏其他甲基转移酶中常见的序列基序，可能代表AdoMet：甲基转移酶的新家族。 DPH5蛋白在大肠杆菌中产生，并显示出对从dph5突变体部分纯化的延伸因子2的甲基化有活性。染色体DPH5基因的无效突变不影响细胞生存力，与其他研究一致，表明双硫酰胺不是细胞存活所必需的。 dph5无效突变体在三个酶促减毒的DT片段的表达中幸免于难，但被完全活性的DT片段A的表达杀死。与这些结果一致，发现dph5无效突变体的延伸因子2具有较弱的ADP-核糖基受体活性。仅在高浓度的片段A存在下才能检测到。

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