Intracellular sites of the synthesis of sweet potato mitochondrial F1ATPase subunits.

Five subunits (α-, β-, γ-, δ- and δ'-subunits) of the six α∼δ'-and ε-subunits) in the F1 portion (F1ATPase) of sweet potato (Ipomoea batatas) mitochondrial adenosine triphosphatase were isolated by an electrophoretic method. The δ- and δ'-subunits were not distinguishable immunologically but showed completely different tryptic peptide maps, indicating that they were different molecular species. In vitro protein synthesis with isolated sweet potato root mitochondria produced only the α-subunit when analyzed with anti-sweet potato F1ATPase antibody reacting with all the subunits except the ε-subunit. Sweet potato root poly(A)(+)RNA directed the synthesis of six polypeptides which were immunoprecipitated by the antibody: two of them immunologically related to the β-subunit and the others to the δ- and δ'-subunits. We conclude that the α-subunit of the F1ATPase is synthesized only in the mitochondria and the β-, δ- and δ'-subunits are in the cytoplasm.