Title: LOCALIZATION OF ACTION OF THE IS<i>50</i>-ENCODED TRANSPOSASE PROTEIN
Abstract:ABSTRACT The movement of the bacterial insertion sequence IS50 and of composite elements containing direct terminal repeats of IS50 involves the two ends of IS50, designated O (outside) and I (inside)...ABSTRACT The movement of the bacterial insertion sequence IS50 and of composite elements containing direct terminal repeats of IS50 involves the two ends of IS50, designated O (outside) and I (inside), which are weakly matched in DNA sequence, and an IS50 encoded protein, transposase, which recognizes the O and I ends and acts preferentially in cis. Previous data had suggested that, initially, transposase interacts preferentially with the O end sequence and then, in a second step, with either an O or an I end. To better understand the cis action of transposase and how IS50 ends are selected, we generated a series of composite transposons which contain direct repeats of IS50 elements. In each transposon, one IS50 element encoded transposase (tnp +), and the other contained a null (tnp -) allele. In each of the five sets of composite transposons studied, the transposon for which the tnp + IS50 element contained its O end was more active than a complementary transposon for which the tnp - IS50 element contained its O end. This pattern of O end use suggests models in which the cis action of transposase and its choice of ends is determined by protein tracking along DNA molecules.Read More