This established that the catalytic site is on F 1 . Thus oligomycin and DCCD inhibit the ATP Synthase by interacting with F o . The complete subunit composition of the ATP Synthase was first established for E. coli, which has an operon that includes genes for all subunits. Each of the three b subunits contains a nucleotide-binding catalytic site. Each a subunit contains a tightly bound ATP, but is inactive in catalysis.
F o is a complex of integral membrane proteins.
Although the number of c subunits is still debated, recent structural studies indicate that there are 10 c subunits in F o . Mammalian F 1 F o is slightly more complex than the bacterial enzyme. Since names were originally assigned based only on apparent molecular weights, some subunits were given different names in different organisms. The bovine d subunit turned out to be homologous to the E. coli e subunit. The bovine e subunit is unique.