A sigma factor is a protein that plays a crucial role in the initiation of transcription in prokaryotes by guiding RNA polymerase to specific promoter regions of DNA. By recognizing and binding to specific sequences within the promoter, the sigma factor facilitates the formation of a stable RNA polymerase-DNA complex, ensuring the correct start point for transcription. Different sigma factors can direct RNA polymerase to different sets of genes, allowing bacteria to respond to various environmental changes.
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