Jh. Chen et al., 2 AMINO-ACID-RESIDUES OF TRANSPOSASE CONTRIBUTING TO DIFFERENTIAL TRANSPOSABILITY OF IS1 ELEMENTS IN ESCHERICHIA-COLI, Journal of bacteriology, 180(19), 1998, pp. 5279-5283
Escherichia coli W3110 contains four types of ISI elements in the chro
mosome. Using an insertion element entrapping system, we collected 116
ISI plasmid insertion mutants, which resulted from a minimum of 26 in
dependent ISI insertion events. All of them had insertions of ISI of t
he IS1A (IS1E and IS1G) type, Inspection of the transposase sequences
of the four ISI types and the ISI of the resistance plasmid R100 showe
d that two amino acid residues, His-193 and Leu-217 of transposase, mi
ght contribute to differential transposability of ISI elements in W311
0. The two amino acid residues of the transposase in IS1A (IS1E and IS
1G) were altered separately by site-directed mutagenesis, and each mut
ant was found to mediate transposition at a frequency about 30-fold lo
wer than that of IS1A (IS1E and IS1G), Thus, the assumption that His-1
93 and Leu-217 of transposase contribute to differential transposabili
ty of ISI elements in W3110 was confirmed.