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Transition state regulatory protein AbrB Bacillus subtilis respond to a multitude of environmental stimuli by using transcription factors called transition state regulators (TSRs). They play an essential role in cell survival by regulating spore formation, competence, and biofilm development. AbrB is one of the most known TSRs, acting as a pleotropic regulator for over 60 different genes where it directly binds to their promoter or regulatory regions. Many other genes are indirectly controlled by AbrB since it is a regulator of other regulatory proteins, including ScoC, Abh, SinR and SigH. Hence, AbrB is considered a global regulatory protein controlling processes such as Bacillus subtilis growth and cell division as well as production of extracellular degradative enzymes, nitrogen utilization and amino acid metabolism, motility, synthesis of antibiotics and their resistant determinants, development of competence, transport systems, oxidative stress response, phosphate metabolism, cell surface components and sporulation. AbrB is a tetramer consisting of identical 94 residue monomers. Its DNA-binding function resides solely in the N-terminal domain (AbrBN) of 53 residues. Although it does not recognize a well-defined DNA base-pairing sequence, instead, it appears to target a very weak pseudo consensus nucleotide sequence, TGGNA-5bp-TGGNA, which allows it to be rather promiscuous in binding. The N-terminal domains of very similar sequences are present in two more Bacillus subtilis proteins, Abh and SpoVT. Mutagenesis studies suggest that the role of the C-terminal domain is in forming multimers. |
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