INTRAGENIC REARRANGEMENTS IN THE MITOCHONDRIAL NADH DEHYDROGENASE SUBUNIT-6 GENE OF VERTEBRATES

We have sequenced the mitochondrial-encoded NADH dehydrogenase subunit 6 gene from 19 species of birds. Comparison of the derived amino-acid sequences in 22 avian species, six mammals, and two fishes, reveals a n intragenic rearrangement in mammals. The C-terminal half of the mamm alian protein includes an internal insertion of 10-15 amino acids and a C-terminal deletion of 8-9 amino acids. Based on comparative sequenc e alignments and hydropathy profile analysis, five hydrophobic segment s (designated I to V) corresponding to transmembrane regions are propo sed. In this structural model of NADH dehydrogenase subunit 6, the mam malian insertion is found in a variable loop region between transmembr ane segments IV and V.