Trypsin activation of native and modified Cry4A toxins.

<p>A. Digestion of native Cry4Aa S1 with 20% trypsin for the specified periods of time resulted in bands of 60, 45 and 20 kDa. The composition of these bands is shown in the schematic diagram at right. Only on prolonged digestion with 20% w/w trypsin (18 and 24 hours) did the 60 kDa intermediate band diminish in intensity. The inset shows the presence of two protein bands in the undigested, purified Cry4Aa-S1, which are assumed to be the 65 and 60 kDa proteins resulting from loss of the N-terminal 36 aa. B. Comparison of the trypsin digestion of the native and modified toxins showed variation in the relative band intensities, with significantly less 60 kDa intermediate in the Cry4Aa 1A and 2A digests. Digestion products separated by SDS-PAGE were transferred to PVDF membrane for western blot detection with anti-Cry4Aa IgG.