Biogenesis of Energy-Yielding ATP Synthase Systems in Crops

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Among subunits of energy-yielding mitochondrial F_1F_0ATPase from plant, F_1- and F_0-9 subunits are encoded by mitochondrial genome. We found that part of pea mitochondrial F_1- subunit gene constitute a repeat sequence involced in homologous recombination, and F_0-9 subunit gene is located 2.1 kb upstream of F_1- gene in an opposite direction. Multiple forms of transcripts were deteced for both of these genes, and datailed transcript mapping and in vitro capping of transcripts suggest that both of these two genes are transcribed from multiple promoter sites.We have purified all of the 6 subunits which constitute the sweet potato root mitochondrial F_1ATPase, and determined N-terminal amino acid sequences of 5 nuclear-encoded subunits. Comparison of these sequences with known amino acid sequencess, we could identify correspondence of all but one, -subunit, of these subunits to F_1F_0ATPase subunits from other organisms. The subunit correspondences thus deduced place plant mitochondrial F_1 at an unique position in the evulution of F_1ATPase.We have cloned full-length cDNAs for the sweet potato F_1- subunit. The amino acid sequence of -subuit precursor deduced from DNA sequence contained 45 amino acid pre-sequence at the N-terminus of the mature subunit. Although the amino acid sequence of the mature part of sweet potato F_1- showed 36 and 24 % homologies with the bovine mitochondrial OSCP and spinach CF_1- , respectively, noobvious sequence homologies in the N-terminal extra peptide region were observed. However, the presequence of the sweet potato F_1- precursor is enriched with basic and hydroxyl amino acids and it can form amphiphilic helical structure. The latter structural feature has been inplied to be inportant for transport of proteins into mitochondria in yeast, fungal and mammalian cells. On the other hand, the transit peptide of the CF_1- does not show this property.