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

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.
Mesh Terms:
Animals, Blotting, Western, Cell Cycle Proteins, Chromosomal Proteins, Non-Histone, DNA Replication, DNA-Binding Proteins, Glutathione Transferase, Humans, Macromolecular Substances, Mice, Nuclear Proteins, Precipitin Tests, Protein Binding, Protein Structure, Quaternary, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Two-Hybrid System Techniques
Genes Cells
Date: May. 01, 2003
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