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. 2001 Apr 24;98(9):4966–4971. doi: 10.1073/pnas.081424898

Figure 2.

Figure 2

Strategy for testing the preferred number of subunit c in E. coli FoF1 complex. (A) System used for coexpression of c3(I30C) and c4(I30C) substituted proteins in one cell. The eight genes of the atp (ATP synthase) operon are deleted from the chromosome of the cell shown. In the scheme shown, the c4 subunit is expressed from a pBR322-derived plasmid carrying genes for the whole atp operon (pWOc4), with transformant cells selected on the basis of plasmid-encoded ampicillin resistance (Ampr). The c3 subunit is expressed by itself from a pACYC184-derived plasmid with transformant cells being selected for via chloramphenicol resistance (Cmr). (B) Coexpression of c3(I30C) and c4(I30C) in the same cell should lead to formation of a c10 decamer if that is the preferred structure in Fo. The figure shows the positions of the I30C-substituted cysteine in the first and last subunit of the c3 trimer and c4 tetramer. The approximate shape of a cross section of subunit c at the position of the I30C substitution is indicated (21). Cys–Cys crosslinking is expected to yield c6, c7, and c10 products.