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    Determinants of Affinity and Activity of the Anti-Sigma Factor AsiA

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    Gilmore_ACS_2010.pdf (4.633Mb)
    Issue Date
    2010-07-27
    Author
    Gilmore, Joshua M.
    Bieber Urbauer, Ramona J.
    Minakhin, Leonid
    Akoyev, Vladimir
    Zolkiewski, Michal
    Sevorinov, Konstantin
    Urbauer, Jeffrey L.
    Publisher
    ACS
    Type
    Article
    Article Version
    Scholarly/refereed, author accepted manuscript
    Rights
    Copyright © 2010 American Chemical Society
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    Abstract
    The AsiA protein is a T4 bacteriophage early gene product that regulates transcription of host and viral genes. Monomeric AsiA binds tightly to the σ70 subunit of Escherichia coli RNA polymerase, thereby inhibiting transcription from bacterial promoters and phage early promoters and co-activating transcription from phage middle promoters. Results of structural studies have identified amino acids at the protomer-protomer interface in dimeric AsiA and at the monomeric AsiA-σ70 interface and demonstrated substantial overlap in the sets of residues that comprise each. Here we evaluate the contributions of individual interfacial amino acid side chains to protomer-protomer affinity in AsiA homodimers, to monomeric AsiA affinity for σ70, and to AsiA function in transcription. Sedimentation equilibrium, dynamic light scattering, electrophoretic mobility shift and transcription activity measurements were used to assess affinity and function of site-specific AsiA mutants. Alanine substitutions for solvent-inaccessible residues positioned centrally in the protomer-protomer interface of the AsiA homodimer – V14, I17, and I40 – resulted in the largest changes in free energy of dimer association, whereas alanine substitutions at other interfacial positions had little effect. These residues also contribute significantly to AsiA-dependent regulation of RNA polymerase activity, as do additional residues positioned at the periphery of the interface (K20 and F21). Notably, the relative contributions of a given amino acid side chain to RNA polymerase inhibition and activation (MotA-independent) by AsiA are very similar in most cases. The mainstay for intermolecular affinity and AsiA function appears to be I17. Our results define the core interfacial residues of AsiA, establish roles for many of the interfacial amino acids, are in agreement with the tenets underlying protein-protein interactions and interfaces, and will be beneficial for a general, comprehensive understanding of the mechanistic underpinnings of bacterial RNA polymerase regulation.
    URI
    http://hdl.handle.net/1808/23684
    DOI
    https://doi.org/10.1021/bi1002635
    Collections
    • Molecular Biosciences Scholarly Works [581]
    Citation
    Gilmore, J. M., Urbauer, R. J. B., Minakhin, L., Akoyev, V., Zolkiewski, M., Severinov, K., & Urbauer, J. L. (2010). Determinants of Affinity and Activity of the Anti-Sigma Factor AsiA. Biochemistry, 49(29), 6143–6154. http://doi.org/10.1021/bi1002635

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    Contact KU ScholarWorks
    785-864-8983
    KU Libraries
    1425 Jayhawk Blvd
    Lawrence, KS 66045
    785-864-8983

    KU Libraries
    1425 Jayhawk Blvd
    Lawrence, KS 66045
    Image Credits
     

     

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