title: Role of the IS50 R proteins in the promotion and control of Tn5 transposition.
abstract: IS50R, the inverted repeat sequence of Tn5 which is responsible for supplying functions that promote and control Tn5 transposition, encodes two polypeptides that differ at their N terminus. Frameshift, in-frame deletion, nonsense, and missense mutations within the N terminus of protein 1 (which is not present in protein 2) were isolated and characterized. The properties of these mutations demonstrate that protein 1 is absolutely required for Tn5 transposition. None of these mutations affected the inhibitory activity of IS50, confirming that protein 2 is sufficient to mediate inhibition of Tn5 transposition. The effects on transposition of increasing the amount of protein 2 (the inhibitor) relative to protein 1 (the transposase) were also analyzed. Relatively large amounts of protein 2 were required to see a significant decrease in the transposition frequency of an element. In addition, varying the co-ordinate synthesis of the IS50 R proteins over a 30-fold range had little effect on the transposition frequency. These studies suggest that neither the wild-type synthesis rate of protein 2 relative to protein 1 nor the amount of synthesis of both IS50 R proteins is the only factor responsible for controlling the transposition frequency of a wild-type Tn5 element in Escherichia coli.
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D009154:Mutation; D009713:Nucleotidyltransferases / Q000378:metabolism*; D013489:Suppression, Genetic; D019895:Transposases
chemical_list: D004251:DNA Transposable Elements; D009713:Nucleotidyltransferases; D019895:Transposases