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Nat Struct Mol Biol. 2016 Oct;23(10):891-898. doi: 10.1038/nsmb.3286. Epub 2016 Aug 29.

Staphylococcal SCCmec elements encode an active MCM-like helicase and thus may be replicative.

Author information

1
Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, USA.
2
Department of Pediatrics, The University of Chicago, Chicago, Illinois, USA.
3
MRSA Research Center, The University of Chicago, Chicago, Illinois, USA.

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) is a public-health threat worldwide. Although the mobile genomic island responsible for this phenotype, staphylococcal cassette chromosome (SCC), has been thought to be nonreplicative, we predicted DNA-replication-related functions for some of the conserved proteins encoded by SCC. We show that one of these, Cch, is homologous to the self-loading initiator helicases of an unrelated family of genomic islands, that it is an active 3'-to-5' helicase and that the adjacent ORF encodes a single-stranded DNA-binding protein. Our 2.9-Å crystal structure of intact Cch shows that it forms a hexameric ring. Cch, like the archaeal and eukaryotic MCM-family replicative helicases, belongs to the pre-sensor II insert clade of AAA+ ATPases. Additionally, we found that SCC elements are part of a broader family of mobile elements, all of which encode a replication initiator upstream of their recombinases. Replication after excision would enhance the efficiency of horizontal gene transfer.

PMID:
27571176
PMCID:
PMC5052118
DOI:
10.1038/nsmb.3286
[Indexed for MEDLINE]
Free PMC Article

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