those of the bacterial enzyme. however, in chloroplasts, the proton motive force is generated not by respiratory electron transport chain but by primary photosynthetic proteins. the synthase has a 40-aa insert in the gamma-subunit to inhibit wasteful activity when dark. mammal the atp synthase isolated from bovine (bos taurus) heart mitochondria is, in terms of biochemistry and structure, the best-characterized atp synthase. beef heart is used as a source for the enzyme because of the high concentration of mitochondria in cardiac muscle. their genes have close homology to human atp synthases. human genes that encode components of atp synthases: atp5a1 atp5b atp5c1, atp5d, atp5e, atp5f1, atp5g1, atp5g2, atp5g3, atp5h, atp5i, atp5j, atp5j2, atp5l, atp5o mt-atp6, mt-atp8 other eukaryotes eukaryotes belonging to some divergent lineages have very special organizations of the atp synthase. a euglenozoa atp synthase forms a dimer with a boomerang-shaped f1 head like other mitochondrial atp synthases, but the fo subcomplex has many unique subunits. it uses cardiolipin. the inhibitory if1 also binds differently, in a way shared with trypanosomatida. archaea archaea do not generally have an f-atpase. instead, they synthesize atp using the a-atpase/synthase, a rotary machine structurally similar to the v-atpase but mainly functioning as an atp synthase. like the bacteria f-atpase, it is believed to also function as an atpase. luca and earlier f-atpase gene linkage and gene order are widely conserved across ancient prokaryote lineages, implying that this system already existed at a date before the last universal common ancestor, the luca.