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| The EMBO Journal
(1998) 17, 4511–4526, doi:10.1093/emboj/17.15.4511 |
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| Protein domains and conformational changes in the activation of RepA, a DNA replication initiator |
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| Rafael Giraldo1, 2, José M. Andreu2 and Ramón Díaz-Orejas1 |
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1 Departamento de Microbiología Molecular, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), c/Velázquez 144, 28006 Madrid, Spain 2 Departamento de Estructura y Función de Proteínas, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC),c/Velázquez 144, 28006 Madrid, Spain To whom correspondence should be addressed Rafael Giraldo, cibgs2q@pinar1.csic.es Received 10 March 1998; Revised 26 May 1998; Accepted 12 June 1998. |
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| Abstract |
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| RepA is the DNA replication initiator protein of the Pseudomonas plasmid pPS10. RepA has a dual function: as a dimer, it binds to an inversely-repeated sequence acting as a repressor of its own synthesis; as a monomer, RepA binds to four directly-repeated sequences to constitute a specialized nucleoprotein complex responsible for the initiation of DNA replication. We have previously shown that a Leucine Zipper-like motif (LZ) at the N-terminus of RepA is responsible for protein dimerization. In this paper we characterize the existence in RepA of two protein globular domains C-terminal to the LZ. We propose that dissociation of RepA dimers into monomers results in a conformational change from a compact arrangement of both domains, competent for binding to the operator, to an extended species that is suited for iteron binding. This model establishes the structural basis for the activation of DNA replication initiators in plasmids from Gram-negative bacteria. |
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| Keywords: conformational changes, DNA replication, initiator activation, protein domains, RepA |
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