Figure 4

IpgC^10-155 Exists as a Dimer in Solution. (A) Samples of purified IpgC (5 mg/mL) proteins were injected onto an analytical gel-filtration column and the elution profiles were compared to a series of known standards to derive an estimation of protein molecular weight (see Additional file 6, Figure S6). The sample identities are IpgC^WT (blue), IpgC^10-155 (red), and IpgC^21-155 (green). The standard mixture is shown as a black dashed line. Aside from the standard injection, all curves were normalized to a maximum peak height of 100 mAU for clarity. (B) Purified samples of IpgC representing both asymmetric (IpgC^1-151) and "head-to-head" dimers (IpgC^10-155) were exposed to the amine-reactive crosslinking agent BS³. Samples were removed at 0, 15, 30, 60, 90, 120, and 240 min following the start of crosslinking, quenched by incubation with Tris, and analyzed for the presence of covalent dimers by SDS-PAGE.