哺乳动物的Mcm2/4/6/7复合体形成一种环形结构。

Mammalian Mcm2/4/6/7 complex forms a toroidal structure.

作者信息

Yabuta Norikazu, Kajimura Naoko, Mayanagi Kouta, Sato Michio, Gotow Takahito, Uchiyama Yasuo, Ishimi Yukio, Nojima Hiroshi

机构信息

Department of Molecular Genetics, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.

出版信息

Genes Cells. 2003 May;8(5):413-21. doi: 10.1046/j.1365-2443.2003.00645.x.

DOI:10.1046/j.1365-2443.2003.00645.x

PMID:12694531

Abstract

BACKGROUND

The Mcm proteins are a family of six homologous proteins (Mcm2-7) that play an important role in DNA replication. They form Mcm4/6/7 and Mcm2/4/6/7 complexes, but their structures are not known.

RESULTS

We found that the human Mcm2/4/6/7 tetramer forms a toroidal structure, with a central cavity about 3-4 nm in diameter. Observations were made using electron microscopy, employing the image analysis of single particles. The most predominant averaged image displayed a toroid harbouring four bulges forming corners, one of which was larger than the others. This structure was very similar to the mouse Mcm2/4/6/7 tetramer that was independently prepared and analysed by electron microscopy. These toroidal structures are distinct from that of the Mcm4/6/7 hexamer, which was also examined by electron microscopy. GST(glutathione S-transferase)-pull down and two hybrid experiments suggest that a putative Mcm6-Mcm6 hinge contributes to the formation of the Mcm7/4/6/6/4/7 heterohexamer.

CONCLUSIONS

The Mcm2/4/6/7 tetramer forms a toroidal structure that is distinct from that of the Mcm4/6/7 hexamer in size and shape.

摘要

背景

Mcm蛋白是由六个同源蛋白（Mcm2 - 7）组成的家族，在DNA复制中起重要作用。它们形成Mcm4/6/7和Mcm2/4/6/7复合物，但其结构尚不清楚。

结果

我们发现人源Mcm2/4/6/7四聚体形成环形结构，中心腔直径约3 - 4纳米。通过电子显微镜观察，采用单颗粒图像分析。最主要的平均图像显示一个环形结构，带有四个形成角的凸起，其中一个比其他的大。该结构与通过电子显微镜独立制备和分析的小鼠Mcm2/4/6/7四聚体非常相似。这些环形结构与同样通过电子显微镜检测的Mcm4/6/7六聚体的结构不同。谷胱甘肽S - 转移酶（GST）下拉实验和双杂交实验表明，一个假定的Mcm6 - Mcm6铰链有助于形成Mcm7/4/6/6/4/7异源六聚体。