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ComK is a DNA-binding transcription activator that triggers the K-state
"ComK is a DNA-binding transcription activator that triggers the K-state (competent state) by upregulating late competence genes required for DNA uptake, processing, and recombination; it also activates its own transcription, forming a positive feedback loop (autoregulation)"
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ComK binds K-boxes as tetramer to activate transcription
"ComK binds promoter K-boxes, typically recognized as a symmetric AT-rich motif AAAA–N5–TTTT; ComK forms a dimer-of-dimers (tetramer) to bind K-box elements and activate transcription at competence promoters including comG and its own comK promoter"
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ComK regulon encompasses at least 165 genes
"Genome-scale analyses identified at least ~165 ComK-activated genes, many in operons preceding identifiable ComK-box motifs, including DNA uptake and recombination loci (e.g., comCDEFG, comFA, comEA, nucA, recA)"
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ComK protein stability is controlled by MecA-ClpC/ClpP proteolysis
"MecA binds ComK and targets it to ClpC/ClpP for ATP-dependent proteolysis; ComS, produced from the quorum-sensing srf operon, competes for MecA and thereby protects/stabilizes ComK"
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Positive feedback creates bistability and bimodal competence
"Positive feedback at PcomK creates a switch-like, bimodal population in which only a subpopulation becomes competent (K-state)"
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Only 5-10% of cells enter the competent K-state
"Approximately 5–10% of cells express comK and enter the K-state under standard competence-inducing conditions"