8S92

Structure of N-terminal domains of Walker B mutated MCM8/9 heterohexamer complex with ADP

Summary for 8S92

• Entry DOI: 10.2210/pdb8s92/pdb
• EMDB information: 40234 40235
• Descriptor: DNA helicase MCM8, DNA helicase MCM9 (2 entities in total)
• Functional Keywords: dna replication, dna repair, dna binding protein
• Biological source: Homo sapiens (human); More
• Total number of polymer chains: 6
• Total formula weight: 663909.89

Authors

Li, C.,Gao, Y. (deposition date: 2023-03-27, release date: 2023-06-07, Last modification date: 2023-08-23)

Primary citation

McKinzey, D.R.,Li, C.,Gao, Y.,Trakselis, M.A.
Activity, substrate preference and structure of the HsMCM8/9 helicase.
Nucleic Acids Res., 51:7330-7341, 2023

PubMed Abstract: The minichromosomal maintenance proteins, MCM8 and MCM9, are more recent evolutionary additions to the MCM family, only cooccurring in selected higher eukaryotes. Mutations in these genes are directly linked to ovarian insufficiency, infertility, and several cancers. MCM8/9 appears to have ancillary roles in fork progression and recombination of broken replication forks. However, the biochemical activity, specificities and structures have not been adequately illustrated, making mechanistic determination difficult. Here, we show that human MCM8/9 (HsMCM8/9) is an ATP dependent DNA helicase that unwinds fork DNA substrates with a 3'-5' polarity. High affinity ssDNA binding occurs in the presence of nucleoside triphosphates, while ATP hydrolysis weakens the interaction with DNA. The cryo-EM structure of the HsMCM8/9 heterohexamer was solved at 4.3 Å revealing a trimer of heterodimer configuration with two types of interfacial AAA+ nucleotide binding sites that become more organized upon binding ADP. Local refinements of the N or C-terminal domains (NTD or CTD) improved the resolution to 3.9 or 4.1 Å, respectively, and shows a large displacement in the CTD. Changes in AAA+ CTD upon nucleotide binding and a large swing between the NTD and CTD likely implies that MCM8/9 utilizes a sequential subunit translocation mechanism for DNA unwinding.

PubMed: 37309874
DOI: 10.1093/nar/gkad508

Experimental method

ELECTRON MICROSCOPY (4.06 Å)