Sorghum mitochondrial atp6: divergent amino extensions to a conserved core polypeptide.

Sorghum mitochondrial atp6 occurs as one copy in the line Tx398 and as two copies in IS1112C. In IS1112C a repeated sequence diverged within the atp6 open reading frames. The two open reading frames (1137 bp, atp6-1; 1002 bp, atp6-2) share an identical conserved region of 756 bp but are flanked 5' by divergent extensions of 246 (atp6-1) or 381 bp (atp6-2). Tx398 carried only atp6-2. The breakpoint of the repeated sequence of the conserved core region corresponds to the amino acid sequence Ser-Pro-Leu-Asp, which is the amino terminus of the proteolytically processed yeast ATP6. The 5' extensions of atp6-1 and atp6-2 were similar to those of rice and maize, respectively. Each open reading is transcribed, however nuclear background influenced transcriptional patterns of atp6-2 in IS1112C.