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Structural studies of AAV2 Rep68 reveal a partially structured linker and compact domain conformation
Structural highlights
FunctionREP68_AAV2S Plays an essential role in the initiation of viral DNA synthesis. Binds specifically to an inverted terminal repeat element (ITR) on the 3' and 5' ends of the viral DNA, where it cleaves a site specifically to generate a priming site for initiation of the synthesis of a complementary strand. Plays also a role as transcriptional regulator, DNA helicase and as key factor in site-specific integration of the viral genome. Inhibits the host cell cycle G1/S and G2/M transitions. These arrests may provide essential cellular factors for viral DNA replication.[1] Publication Abstract from PubMedAdeno-associated virus (AAV) nonstructural proteins Rep78 and Rep68 carry out all DNA transactions that regulate the AAV life cycle. They share two multifunctional domains: an N-terminal origin binding/nicking domain (OBD) from the HUH superfamily and a SF3 helicase domain. A short linker of approximately 20 amino acids that is critical for oligomerization and function connects the two domains. Although X-ray structures of the AAV5 OBD and AAV2 helicase domains have been determined, information about the full-length protein and linker conformation is not known. This article presents the solution structure of AAV2 Rep68 using small-angle X-ray scattering (SAXS). We first determined the X-ray structures of the minimal AAV2 Rep68 OBD and of the OBD with the linker region. These X-ray structures reveal novel features that include a long C-terminal alpha-helix that protrudes from the core of the protein at a 45 degrees angle and a partially structured linker. SAXS studies corroborate that the linker is not extended, and we show that a proline residue in the linker is critical for Rep68 oligomerization and function. SAXS-based rigid-body modeling of Rep68 confirms these observations, showing a compact arrangement of the two domains in which they acquire a conformation that positions key residues in all domains on one face of the protein, poised to interact with DNA. Structural Studies of AAV2 Rep68 Reveal a Partially Structured Linker and Compact Domain Conformation.,Musayev FN, Zarate-Perez F, Bardelli M, Bishop C, Saniev EF, Linden RM, Henckaerts E, Escalante CR Biochemistry. 2015 Sep 29;54(38):5907-19. doi: 10.1021/acs.biochem.5b00610. Epub , 2015 Sep 14. PMID:26314310[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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