Monroe Danny S, Leitzel Adelaide K, Klein Hannah L, Matson Steven W
Department of Biology, University of North Carolina at Chapel Hill, NC 27599-2380, USA.
Yeast. 2005 Dec;22(16):1269-86. doi: 10.1002/yea.1313.
The HMI1 gene encodes a DNA helicase that localizes to the mitochondria and is required for maintenance of the mitochondrial DNA (mtDNA) genome of Saccharomyces cerevisiae. Identified based on its homology with E. coli uvrD, the HMI1 gene product, Hmi1p, has been presumed to be involved in the replication of the 80 kb linear S. cerevisiae mtDNA genome. Here we report the purification of Hmi1p to apparent homogeneity and provide a characterization of the helicase reaction and the ATPase reaction with regard to NTP preference, divalent cation preference and the stimulatory effects of different nucleic acids on Hmi1p-catalysed ATPase activity. Genetic complementation assays indicate that mitochondrial localization of Hmi1p is essential for its role in mtDNA metabolism. The helicase activity, however, is not essential. Point mutants that lack ATPase/helicase activity partially complement a strain lacking Hmi1p. We suggest several possible roles for Hmi1p in mtDNA metabolism.
HMI1基因编码一种定位于线粒体的DNA解旋酶，它是酿酒酵母线粒体DNA（mtDNA）基因组维持所必需的。基于其与大肠杆菌uvrD的同源性鉴定出HMI1基因，其基因产物Hmi1p被推测参与80 kb线性酿酒酵母mtDNA基因组的复制。在此，我们报道了将Hmi1p纯化至表观均一，并对解旋酶反应和ATP酶反应在NTP偏好、二价阳离子偏好以及不同核酸对Hmi1p催化的ATP酶活性的刺激作用方面进行了表征。遗传互补分析表明，Hmi1p的线粒体定位对其在mtDNA代谢中的作用至关重要。然而，解旋酶活性并非必需。缺乏ATP酶/解旋酶活性的点突变体部分互补缺失Hmi1p的菌株。我们提出了Hmi1p在mtDNA代谢中的几种可能作用。
