The trans-activation domain of the sporulation response regulator Spo0A revealed by X-ray crystallography.
Sporulation in Bacillus involves the induction of scores of genes in a temporally and spatially co-ordinated programme of cell development. Its initiation is under the control of an expanded two-component signal transduction system termed a phosphorelay. The master control element in the decision to sporulate is the response regulator, Spo0A, which comprises a receiver or phosphoacceptor domain and an effector or transcription activation domain. The receiver domain of Spo0A shares sequence similarity with numerous response regulators, and its structure has been determined in phosphorylated and unphosphorylated forms. However, the effector domain (C-Spo0A) has no detectable sequence similarity to any other protein, and this lack of structural information is an obstacle to understanding how DNA binding and transcription activation are controlled by phosphorylation in Spo0A. Here, we report the crystal structure of C-Spo0A from Bacillus stearothermophilus revealing a single alpha-helical domain comprising six alpha-helices in an unprecedented fold. The structure contains a helix-turn-helix as part of a three alpha-helical bundle reminiscent of the catabolite gene activator protein (CAP), suggesting a mechanism for DNA binding. The residues implicated in forming the sigmaA-activating region clearly cluster in a flexible segment of the polypeptide on the opposite side of the structure from that predicted to interact with DNA. The structural results are discussed in the context of the rich array of existing mutational data.
Lewis
R J
RJ
Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK.
Krzywda
S
S
Brannigan
J A
JA
Turkenburg
J P
JP
Muchová
K
K
Dodson
E J
EJ
Barák
I
I
Wilkinson
A J
AJ
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D001411:Geobacillus stearothermophilus / Q000737:chemistry*; D019077:Helix-Turn-Helix Motifs; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D012996:Solutions; D013171:Spores, Bacterial; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism; D015533:Transcriptional Activation
D001426:Bacterial Proteins; D012996:Solutions; C080950:Spo0A protein, Bacillus subtilis; D014157:Transcription Factors