Affiliation:
1. Institute of Molecular and Cellular Biosciences, University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
Abstract
ABSTRACT
Transposases encoded by various transposable DNA elements and retroviral integrases belong to a family of proteins with three conserved acidic amino acids, D, D, and E, constituting the D-D-E motif that represents the active center of the proteins. IS
1
, one of the smallest transposable elements in bacteria, encodes a transposase which has been thought not to belong to the family of proteins with the D-D-E motif. In this study, we found several IS
1
family elements that were widely distributed not only in eubacteria but also in archaebacteria. The alignment of the transposase amino acid sequences from these IS
1
family elements showed that out of 14 acidic amino acids present in IS
1
transposase, three (D, D, and E) were conserved in corresponding positions in the transposases encoded by all the elements. Comparison of the IS
1
transposase with other proteins with the D-D-E motif revealed that the polypeptide segments surrounding each of the three acidic amino acids were similar. Furthermore, the deduced secondary structures of the transposases encoded by IS
1
family elements were similar to one another and to those of proteins with the D-D-E motif. These results strongly suggest that IS
1
transposase has the D-D-E motif and thus belongs to the family of proteins with the D-D-E motif. In fact, mutant IS
1
transposases with an amino acid substitution for each of the three acidic amino acids possibly constituting the D-D-E motif were not able to promote transposition of IS
1
, supporting this hypothesis. The D-D-E motif identified in IS
1
transposase differs from those in the other proteins in that the polypeptide segment between the second D and third E in IS
1
transposase is the shortest, 24 amino acids in length. Because of this difference, the presence of the D-D-E motif in IS
1
transposase has not been discovered for some time.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
25 articles.
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