Abstract
Mitochondrial changes such as tight coupling of the mitochondria have facilitated sustained oxygen and respiratory activity in haemoglobin-less icefish of the Channichthyidae family. We aimed to characterise features in the sequence and structure of the proteins directly involved in proton transport, which have potential physiological implications. ATP synthase subunit a (ATP6) and subunit 8 (ATP8) are proteins that function as part of the F0 component (proton pump) of the F0F1complex. Both proteins are encoded by the mitochondrial genome and involved in oxidative phosphorylation. To explore mitochondrial sequence variation for ATP6 and ATP8 we analysed sequences from C. gunnari and C. rastrospinosus and compared them with their closely related red-blooded species and eight other vertebrate species. Our comparison of the amino acid sequence of these proteins reveals important differences that could underlie aspects of the unique physiology of the icefish. In this study we find that changes in the sequence of subunit a of the icefish C. gunnari at position 35 where there is a hydrophobic alanine which is not seen in the other notothenioids we analysed. An amino acid change of this type is significant since it may have a structural impact. The biology of the haemoglobin-less icefish is necessarily unique and any insights about these animals will help to generate a better overall understanding of important physiological pathways.
Highlights
The oceans which surround Antarctica, and their sub-zero temperatures provide a home to fish of the suborder Notothenioidei—a prime example of a marine species flock.Notothenioids are renowned for their physiological adaptations to cold temperatures
When we look at the codon alignment of the ATP6 gene, serine is encoded by codon TCT predominantly at position 39 for all the species except T. bernacchii and H. sapiens and the alanine for the species C. gunnari is encoded by GCT
We present our analyses highlighting differences in sequence and structure observed in the two proteins of complex V, ATP8 and ATP6, encoded by mitochondrial DNA (mtDNA) between the red- and white blooded species of suborder Notothenioidei
Summary
The oceans which surround Antarctica, and their sub-zero temperatures provide a home to fish of the suborder Notothenioidei—a prime example of a marine species flock. Notothenioids are renowned for their physiological adaptations to cold temperatures. This includes the ability to synthesise antifreeze glycoproteins (AFGP) and antifreeze-potentiating proteins (AFPP) [1]. The capacity to synthesise antifreeze glycopeptides (AFGPs) is a biochemical adaptation that enabled the Notothenioidei to colonize and thrive in the extreme polar environment [2].
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