FIGURE 4.

Analysis of cross-links in complexes A and H using [APB⁺⁹B]-pre-mRNA-S. (A) Gradient profile of complexes H and A. Incubation at 0°C or 30°C was stopped after 15 min, and the reaction mixture was centrifuged in a TST41.14 rotor. Complex H was found in fractions 7–10 from the 0°C incubation, and narrowed to fractions 6–7 when incubation conditions (30°C) produced complex A as well; the latter was found in fractions 11–14. (B) Cross-linking profile of the gradient fractions. Twenty microliters of a cross-linked and T1-digested 500 μL gradient fraction or 10 μL of the starting material of one preparative reaction, cross-linked without centrifugation (input, “i”), were separated on 10% SDS–polyacrylamide gel. (M) The molecular weights of the prestained marker are indicated at right. For the input, a shorter exposure is shown.