The sequences of the left end of the nisin-sucrose transposon Tn5481 in Lac
tococcus lactis subsp. lactis N8, the adjacent 1.5 kb chromosomal region up
stream of the junction site as well as a 5.0 kb region downstream of the ni
sZBTCIPRKFEG genes within the transposon have been determined. In the upstr
eam chromosomal region, an incomplete open reading frame encoding a protein
with strong N-terminal homology to the low-affinity branched chain amino a
cid carriers was identified. Within the transposon, downstream of the nisin
gene cluster, a 186 bp almost identical copy of the left hand sequence was
located. Further downstream, four new open reading frames were found. The
codon usage in these reading frames as well as the G+C content of the regio
n are clearly different from those of the nisin genes, suggesting that the
functionally unrelated areas of Tn5481 are gathered from different origins
during the evolution of the transposon.