dehydrogenase activity by preventing access to the enzyme; however, it is unclear why the activity of propionaldehyde dehydrogenase exhibited an increase without a concomitant increase in diol dehydratase activity. The 12,000 x g spin that followed the detergent treatment resulted in a slight loss of activity which is most likely due to the pelleting of organelles with cell debris. Like diol dehydratase activity, the activity of propionaldehyde dehydrogenase showed a significant increase after high speed centrifugation and clarification (0.50 to 2 U/mg) and a 2-fold increase after separation on a sucrose gradient (2 to 4 U/mg). The approximate 13.6-fold increase of propionaldehyde dehydrogenase activity observed for the complete purification is consistent with idea that polyhedral organelles constitute approximately 10% of the total cell protein.

Western Blot Analysis of Purified Polyhedral Organelles

      To examine their composition, western blots were performed on purified polyhedral organelles using antisera against diol dehydratase (PduCDE) and the PduAJOP proteins. An antiserum previously shown to be specific for the PduA protein (Havemann et al. 2002) recognized a single band at 11 kDa (Figure 4-3, lane 3). This is near the expected value for PduA (9.6 kDa) indicating that this protein is a component of the purified organelles. A second antiserum, shown in a prior study to react with both the PduA and PduJ proteins (Havemann et al. 2002), recognized one band at 11 kDa (PduA) as well as a second band near the predicted molecular mass of PduJ (10.6 kDa) (Figure 43, lane 4). Thus, it appears that the PduJ protein is also an organelle component.

      In further serological tests, PduO and PduP antisera were found to recognize

proteins of 39 and 52 kDa, as well as some additional proteins. (Figure 4-3, lanes 6 and