title: Staphylococcal SCCmec elements encode an active MCM-like helicase and thus may be replicative.
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.
authors: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, USA.
authors: Ignacio
authors: I
authors: Mir-Sanchis
authors: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, USA.
authors: Christina A
authors: CA
authors: Roman
authors: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, USA.
authors: Agnieszka
authors: A
authors: Misiura
authors: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, USA.
authors: Ying Z
authors: YZ
authors: Pigli
authors: Department of Pediatrics, The University of Chicago, Chicago, Illinois, USA.|MRSA Research Center, The University of Chicago, Chicago, Illinois, USA.
authors: Susan
authors: S
authors: Boyle-Vavra
authors: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, USA.
authors: Phoebe A
authors: PA
authors: Rice
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002876:Chromosomes, Bacterial / Q000235:genetics*; D018360:Crystallography, X-Ray; D004265:DNA Helicases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004261:DNA Replication; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D055624:Methicillin-Resistant Staphylococcus aureus / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008958:Models, Molecular; D016366:Open Reading Frames; D011487:Protein Conformation; D000072417:Protein Domains; D055503:Protein Multimerization; D013203:Staphylococcal Infections / Q000382:microbiology
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D000251:Adenosine Triphosphatases; D004265:DNA Helicases