Evidence for a repeating domain in type I restriction enzymes.
The primary structures of the recognition subunit (hsdS) in type I restriction enzymes from three isolates of Escherichia coli were compared and aligned by use of amino acid physical properties. A repeating domain was found in each of the subunits suggesting a pseudo-dimeric structure. Secondary structure predictions delineated two helical regions in each domain which suggested that the recognition subunits may act in a fashion similar to that proposed for repressor and activator molecules; namely, interaction with double-stranded DNA through helices and in two successive major grooves on the same DNA side. One helical motif could provide the specific recognition site and the other, the restriction site.
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D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001665:Binding Sites; D004262:DNA Restriction Enzymes / Q000032:analysis*; D004926:Escherichia coli / Q000201:enzymology*; D011953:Receptors, Cyclic AMP / Q000032:analysis
D000596:Amino Acids; D011953:Receptors, Cyclic AMP; D004262:DNA Restriction Enzymes