... examined using the insulin precipitation assay. In the noncatalyzed assay, the disulfides of insulin arereduced by dithiothreitol, causing the aggregation andprecipitation of the B-chain of insulin, ... B-chain significantly,decreasing the lag-phase (Fig. 2A). When bacitracin wasincluded with PDI, the lag-phase of the insulin precipita-tion increased (Fig. 2A), with the effects increasing with increasing ... bacitracin is known to bind. These metal ions couldbe coordinated by the active site cysteines of the catalyticdomains of PDI, decreasing their activity. In addition,other thiols present in the...