Sigma factor: Difference between revisions
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===Domains=== | ===Domains=== | ||
Each σ is composed of a variable number of structured domains. The simplest σ-factors have two domains, few have three, and others, called '''housekeeping σ-factors''' have 4 domains. Each of these domains has DNA-binding determinants, or motifs that recognize specific sequences and conformations in DNA. Most commonly, these recognized motifs occur at the -35 and -10 locations upstream of the +1 site. | Each σ is composed of a variable number of structured domains. The simplest σ-factors have two domains, few have three, and others, called '''housekeeping σ-factors''' have 4 domains. Each of these domains has DNA-binding determinants, or motifs that recognize specific sequences and conformations in DNA. Most commonly, these recognized motifs occur at the -35 and -10 locations upstream of the +1 site. One such DNA binding motif, '''the helix-turn-helix motif''' (HTH), helps specifically recognize DNA promoters at both the -35 and -10 positions. This HTH motif, used by most σ-factors, maintains its specificity and accuracy by binding in the '''major groove''' of DNA, where it can interact with the base pairs in the DNA double-helix. In many prokaryotes, these portions of DNA maintain consensus adenosine and thymine sequences, such as TATAAT. | ||
== Relevance == | == Relevance == | ||
