Molecular architecture of a multifunctional MCM complex

June Sanchez-Berrondo; Pablo Mesa; Arkaitz Ibarra; Maria I Martínez-Jiménez; Luis Blanco; Juan Méndez; Jasminka Boskovic; Guillermo Montoya

doi:10.1093/nar/gkr831

Molecular architecture of a multifunctional MCM complex

Nucleic Acids Res. 2012 Feb;40(3):1366-80. doi: 10.1093/nar/gkr831. Epub 2011 Oct 7.

Authors

June Sanchez-Berrondo¹, Pablo Mesa, Arkaitz Ibarra, Maria I Martínez-Jiménez, Luis Blanco, Juan Méndez, Jasminka Boskovic, Guillermo Montoya

Affiliation

¹ Structural Biology and Biocomputing Programme, Macromolecular Crystallography Group, Spanish National Cancer Research Center (CNIO), c/Melchor Fdez. Almagro 3, 28029-Madrid, Spain.

Abstract

DNA replication is strictly regulated through a sequence of steps that involve many macromolecular protein complexes. One of them is the replicative helicase, which is required for initiation and elongation phases. A MCM helicase found as a prophage in the genome of Bacillus cereus is fused with a primase domain constituting an integrative arrangement of two essential activities for replication. We have isolated this helicase-primase complex (BcMCM) showing that it can bind DNA and displays not only helicase and primase but also DNA polymerase activity. Using single-particle electron microscopy and 3D reconstruction, we obtained structures of BcMCM using ATPγS or ADP in the absence and presence of DNA. The complex depicts the typical hexameric ring shape. The dissection of the unwinding mechanism using site-directed mutagenesis in the Walker A, Walker B, arginine finger and the helicase channels, suggests that the BcMCM complex unwinds DNA following the extrusion model similarly to the E1 helicase from papillomavirus.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adenosine Diphosphate / chemistry
Adenosine Triphosphatases / chemistry
Adenosine Triphosphatases / metabolism
Adenosine Triphosphate / analogs & derivatives
Adenosine Triphosphate / chemistry
Adenosine Triphosphate / metabolism
Bacillus cereus / enzymology
Bacterial Proteins / chemistry*
Bacterial Proteins / genetics
Bacterial Proteins / metabolism
Bacterial Proteins / ultrastructure
DNA / metabolism
DNA Helicases / chemistry*
DNA Helicases / genetics
DNA Helicases / metabolism
DNA Helicases / ultrastructure
DNA Primase / chemistry*
DNA Primase / genetics
DNA Primase / metabolism
DNA Primase / ultrastructure
DNA, Single-Stranded / chemistry
DNA, Single-Stranded / metabolism
DNA-Directed DNA Polymerase / metabolism
Deoxyribonucleotides / metabolism
Models, Molecular
Mutation
Protein Structure, Tertiary

Substances

Bacterial Proteins
DNA, Single-Stranded
Deoxyribonucleotides
adenosine 5'-O-(3-thiotriphosphate)
Adenosine Diphosphate
Adenosine Triphosphate
DNA
DNA Primase
DNA-Directed DNA Polymerase
Adenosine Triphosphatases
DNA Helicases