FIG. 3.

Effect of pepsin on Ad41 and Ad37 fiber heads. Treatment with pepsin (pepsin-fiber head = 1:2 [wt/wt]) was done at pH 3, room temperature. Samples were taken at 6 different time points and analyzed by SDS PAGE and Coomassie staining on a 13.5% Tris-Tricine-polyacrylamide gel or 17% SDS/polyacrylamide gel. Digestion products of Ad41 fiber head were loaded on a Superdex 75 column (Pharmacia). Lane T/min 0′ represents the respective fiber prior to incubation with pepsin. Sizes corresponding to marker proteins are indicated. (A) Ad37 fiber head visualized on a 13.5% Tris-Tricine-polyacrylamide gel. Arrow 1, full-length protein. Arrow 5, pepsin protease. (B) Ad41 short fiber head visualized on a 13.5% Tris-Tricine-polyacrylamide gel. Arrow 2, full-length protein. Arrow 3, digestion products containing N-terminal residues. Arrow 4, digestion products containing the C terminus from Ile-341. Arrow 5, pepsin protease. (C) Ad41 short fiber head after 2 h digestion with pepsin (fiber head-pepsin = 2:1 [wt/wt]) at 20°C was loaded onto a Superdex 75 column. Peak fractions were visualized on a 13.5% Tris-Tricine-polyacrylamid gel. (Lanes 2 to 6). Arrow 3, digestion products containing N-terminal residues. Arrow 4, digestion products containing the C terminus from Ile-341. (D) Ad37 fiber head visualized on a 17% SDS/polyacrylamide gel. Arrow 1, full-length protein. Arrow 5, pepsin protease. (E) Ad41 short fiber head visualized on a 17% SDS/polyacrylamide gel. Arrow 2, full-length protein. Arrow 3, digestion products containing N-terminal residues. Arrow 5, pepsin protease. Note that the C-terminal fragment is too small to be visualized on this gel. F: Lane 1, arrow 6: Ad41 short fiber head crystals grown at pH 5 after washing, dissolving in SDS sample loading buffer, and visualization on a 15% SDS/polyacrylamide gel.