FIG. 4.

Analysis of the quaternary structure of the AT C-terminal domains in vivo and in vitro. (A and B) Cross-linking with DSP of HE-ATs expressed in E. coli to determine the formation of oligomeric complexes of AT C-terminal domains in vivo. DSP-treated (+) and untreated (−) samples were subjected to nonreducing SDS-PAGE, and the Western blot was probed with anti-E tag MAb. Samples incubated with the reducing agent 2-ME are indicated (+). (C) Blue native PAGE of purified HE-ATs from the outer membrane of E. coli bacteria. The polypeptides were detected by Western blotting with an anti-E tag MAb. The masses of protein standards are shown on the left (in kDa).