In vitro helicase
activity of hHcsA expressed in E.coli. (A)
A standard helicase assay was carried out utilizing a 50 bp duplex
substrate and increasing amounts of purified hHcsA (fraction V).
Inhibition at higher protein concentrations was presumably due to
salt. (B) Analysis of the polarity of
translocation. A time-course analysis of helicase activity (100
ng HcsA fraction III) using the directionality substrate, as described
in Materials and Methods, was carried out in the presence of 250 ng
RPA. Lanes 1–5 correspond to assay points in which the
30mer duplex is 5′-end-labeled, while
lanes 6–10 correspond to assay points in which the 45mer
duplex is 3′-end-labeled. Lane 1, 0
min; lane 2, 1 min; lane 3, 2 min; lane 4, 5 min; lane 5, heat denatured
substrate labeled at the 30mer duplex end; lane 6, heat denatured
substrate labeled at the 45mer duplex end; lane 7, 0 min; lane 8,
1 min; lane 9, 2 min; lane 10, 5 min.