CASP3 Target T0066

This is a complex of SinR (chain A) and SinI (chain B). Predictions in all formats for individual chains should be submitted as either T0064 or T0065.

Only predictions of interchain residue-residue contacts and atomic coordinate predictions (in TS format) for the complex (consisting of both chains) should be submitted as T0066.

1. Protein Name: SinI and SinR
2. Organism Name: Bacillus subtilis
3. Number of amino acids (approx): 57 and 111
4. Accession number: P23308 and P06533
5. Sequence Database: Swiss-Prot
6. Amino acid sequence: SinI

MKNAKQEHFELDQEWVELMVEAKEANISPEEIRKYLLLNKKSAHPGPAAR
SHTVNPF

##################################################

SinR

MIGQRIKQYRKEKGYSLSELAEKAGVAKSYLSSIERNLQTNPSIQFLEKV
SAVLDVSVHTLLDEKHETEYDGQLDSEWEKLVRDAMTSGVSKKQFREFLD
YQKWRKSQKEE
7. Homologous Sequence of known structure: no
8. Current state of the experimental work: X-ray structure solved and refined of the heterodimeric
complex of SinI and SinR. Manuscript submitted.
9. Interpretable map?: yes
10. Estimated date of chain tracing completion: finished
11. Estimated date of public release of structure: september 1998
12. Additional Information
13. Name: Dr. Rick Lewis
14. Mailing address: Department of Chemistry
University of York, York
North Yorkshire YO1 5DD
U.K.
15. Telephone: +44 (0)1904 432590
16. Fax: +44 (0)1904 410519
17. Email: rick@yorvic.york.ac.uk
18. Source of information about experiment: Email

Note: Some structural information regarding structure of the target has been released in the form of an abstract. The abstract is appended below.

THE CRYSTAL STRUCTURE OF SINR, AN INHIBITOR OF SPORULATION IN BACILLUS SUBTILIS IN COMPLEX WITH ITS ANTAGONIST SINI
R.J. Lewis, J.A. Brannigan, W. Offen, I. Smith & A.J. Wilkinson
Department of Chemistry, University of York, York. U.K.
_________________________________________________________________

Amongst a panoply of molecular components which regulate the entry of Bacillus subtilis into the sporulation pathway are the proteins of the sin (sporulation inhibition) operon. The sin region encodes two proteins SinR (Mr = 14,000) and SinI (Mr = 6,000). SinR is a DNA binding protein which negatively regulates the transcription of genes, including spo0A, spoIIA, spoIIE and spoIIG, in late phase Bacillus growth. The effects exerted by SinR must be overcome in order for the sporulation process to proceed. SinI, which is encoded on the same operon as SinR but subject to different regulatory signals, acts as an antagonist of SinR through direct binding of the two proteins. This interaction involves an interesting subunit reorganisation; equilibrium sedimentation experiments indicate that SinR is a tetramer and that SinI as also multimeric. In contrast, the SinR-SinI complex is a heterodimer.

We have recently solved the crystal structure of SinR in complex with SinI to 1.9 Å spacing. The phases were calculated using data collected from two selenium derivatives, in the first of these SinR contained seleno- methionine, in the second of these SinI contained selenomethionine. In the crystal, the SinI-SinR complex is, as expected, a heterodimer. SinR consists of an N-terminal 66 residue domain with very high structural similarity to the DNA binding domain of bacteriophage 434 and [lambda] CI (repressor) proteins including a helix-turn-helix DNA binding motif. A somewhat disordered region of 10 or so residues connects this domain to the C-terminal 40 residues which are involved in interactions with SinI. The interactions between SinI and SinR appear to be strong with a pair of helices from each partner interdigitating to form a significant hydrophobic core. Most interestingly, it has been noted that the central 30 residues of SinI and the 30 residues towards the C-terminus of SinR have closer sequence similarity to one another than either has to any other sequence in the database. This suggests that the interactions among SinR monomers in the tetramer may be akin to those between SinR and SinI in the heterodimer.

Related Files

Template Sequence file

Template PDB file