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Dimer-induced signal propagation in Spo0A

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JournalMolecular Microbiology
DatePublished - Aug 2004
Issue number3
Volume53
Number of pages14
Pages (from-to)829-842
Original languageEnglish

Abstract

Spo0A, the response regulator protein controlling the initiation of sporulation in Bacillus, has two distinct domains, an N-terminal phosphoacceptor (or receiver) domain and a C-terminal DNA-binding (or effector) domain. The phosphoacceptor domain mediates dimerization of Spo0A on phosphorylation. A comparison of the crystal structures of phosphorylated and unphosphorylated response regulators suggests a mechanism of activation in which structural changes originating at the phosphorylatable aspartate extend to the alpha(4)beta(5)alpha(5) surface of the protein. In particular, the data show an important role in downstream signalling for a conserved aromatic residue (Phe-105 in Spo0A), the conformation of which alters upon phosphorylation. In this study, we have prepared a Phe-105 to Ala mutant to probe the contribution of this residue to Spo0A function. We have also made an alanine substitution of the neighbouring residue Tyr-104 that is absolutely conserved in the Spo0As of spore-forming Bacilli. The spo0A(Y104A) and spo0A(F105A) alleles severely impair sporulation in vivo. In vitro phosphorylation of the purified proteins by phosphoramidate is unaffected, but dimerization and DNA binding are abolished by the mutations. We have identified intragenic suppressor mutations of spo0A(F105A) and shown that these second-site mutations in the purified proteins restore phosphorylation-dependent dimer formation. Our data support a model in which dimerization and signal transduction between the two domains of Spo0A are mediated principally by the alpha(4)beta(5)alpha(5) signalling surface in the receiver domain.

Bibliographical note

© 2004 Blackwell Publishing Ltd. This is an electronic version of an article published in Molecular Microbiology: complete citation information for the final version of the paper, as published in the print edition of Molecular Microbiology, is available on the Blackwell Synergy online delivery service, accessible via the journal's website at http://www.blackwellpublishing.com/journal.asp?ref=0950-382X or www.blackwell-synergy.com

    Research areas

  • RESPONSE REGULATOR SPO0A, SPORULATION TRANSCRIPTION FACTOR, FIXJ RECEIVER DOMAIN, BACILLUS-SUBTILIS, MOLECULAR RECOGNITION, SPOOA, PHOSPHORYLATION, PROTEIN, PHOSPHORELAY, INITIATION

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