1b0n
From Proteopedia
SINR PROTEIN/SINI PROTEIN COMPLEX
Structural highlights
Function[SINR_BACSU] Negative as well as positive regulator of alternate developmental processes that are induced at the end of vegetative growth in response to nutrient depletion. Binds to the alkaline protease (aprE) gene at two sites. Also acts as a repressor of the key sporulation gene spo0A. Negatively regulates transcription of the eps operon, which is responsible for the biosynthesis of an exopolysaccharide involved in biofilm formation; therefore it could govern the transition between a state in which bacteria swim or swarm and a state in which bacteria assemble into multicellular communities. Acts with Hpr as a corepressor of epr expression. Also negatively regulates transcription of the lutABC operon, which is required for lactate utilization. Repressor activity is regulated by SinI.[1] [2] [3] [4] [SINI_BACSU] Acts as an antagonist to SinR. SinI prevents SinR from binding to its target sequence on the gene for AprE. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedSpore formation is an extreme response of some bacteria to adversity. In Bacillus subtilis the proteins of the sin, sporulation inhibition, region form a component of an elaborate molecular circuitry that regulates the commitment to sporulation. SinR is a tetrameric repressor protein that binds to the promoters of genes essential for entry into sporulation and prevents their transcription. This repression is overcome through the activity of SinI, which disrupts the SinR tetramer through the formation of a SinI-SinR heterodimer. The interactions governing this curious quaternary transition are revealed in the crystal structure of the SinI-SinR complex. The most striking, and unexpected, finding is that the tertiary structure of the DNA-binding domain of SinR is identical with that of the corresponding domains of the repressor proteins, CI and Cro, of bacteriophage 434 that regulate lysis/lysogeny. This structural similarity greatly exceeds that between SinR and any bacterial protein or between the 434 repressor proteins and their homologues in the closely related bacteriophage lambda. The close evolutionary relationship implied by the structures of SinR and the 434 repressors provokes both comparison of their functions and a speculative consideration of the intriguing possibility of an evolutionary link between the two adaptive responses, sporulation and prophage induction. An evolutionary link between sporulation and prophage induction in the structure of a repressor:anti-repressor complex.,Lewis RJ, Brannigan JA, Offen WA, Smith I, Wilkinson AJ J Mol Biol. 1998 Nov 13;283(5):907-12. PMID:9799632[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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