Fig. 2.

Reaction with Chi⁺ DNA sensitizes RecC to cleavage by trypsin. (a) RecBCD was treated for 1 min with trypsin (3.2, 10, 32, 100, 320,or 1000 nM) during reaction on phage lambda DNA (48.5 kb) lacking (Chi⁰) orbearinga Chi site 3.5 kb from the right end (Chi⁺). RecC polypeptides and their fragments were detected by Western blots using polyclonal antibodies. (b) As in (a) but showing polypeptides detected with anti-RecB polyclonal antibodies. (c) Quantification of Chi⁰ data in (a), with fragments identified by their molecular mass in kilodaltons (kDa). 91 + 55, sum of the 91-kDa and 55-kDa fragments, the latter likely resulting from trypsin cleavages at both sites 1 and 2. (d) Quantification of Chi⁺ data in (a). Diagrams at the bottoms of (a) and (b) indicate the positions of trypsin cleavages and the designations of the tryptic fragments.