FIG. 4.
Detection of biotin-containing cleavage products of heterodimers. Subunit exchange between NtrCD86CFe and NtrCD86CBio (2:1) yielded the heterodimers represented in panel C. All samples were phosphorylated and cleaved. (A) Biotin-containing cleavage fragments from heterodimers (4.5 μg of total protein) were detected with AP-streptavidin (lane 2). Cleavage fragments from NtrCD86CFe (10 μg) were stained with Coomassie blue to serve as markers (lane 1). (B) Antibodies directed against the C terminus of NtrC were used to detect fragments from heterodimers (4.5 μg of total protein; lane 2) and from the control NtrCD86CFe (3 μg; lane 1). (C) Heterodimers (see above).