Abstract

The amino-terminal domain of bacteriophage λ integrase recognizes specific DNA sequences called arm-type sites. To study the structural and functional relationships of the integras armtype DNA binding domains were confirmed by gel mobility-shift assay. The polypeptides were subjected to circular dichroism spectroscopy to estimate the amount of secondary structures they contain Based upon analyses of circular dichroism spectra and comparison with predicted secondary structural compositions, it was estimated that the amino terminal domain of integrase in an aqueous solution was composed of a little α-helical region. The helical content increased with an increasing amount of ethanol, an α-helix inducer. This indicates that its conformation can be changed to a form with higher content of α-helical structure under a certain condition.

• Keywords: Integrase; lambda; arm-Type DNA binding; secondary structure; circular dichroism; DNA binding domain