Structure-Related Differences between Cytochrome Oxidase I Proteins in a Stable Heteroplasmic Mitochondrial System

Area of Science:

• Mitochondrial genomics
• Evolutionary biology
• Biochemistry

Background:

• Bivalves possess two distinct mitochondrial DNA genomes: the F genome (female) and M genome (male).
• Cytochrome oxidase I (COI) is a crucial protein in mitochondrial respiration.

Purpose of the Study:

• To investigate the differences in amino acid properties between F and M COI proteins in bivalves.
• To explore the evolutionary mechanisms driving these observed protein variations.

Main Methods:

• Comparative analysis of amino acid sequences and properties (hydrophobicity, helicity) of F and M COI proteins across bivalve species.
• Evaluation of evolutionary pressures (purifying selection, positive selection, genetic drift).

Main Results:

• Significant differences in amino acid properties, especially hydrophobicity and helicity, were found between F and M COI proteins.
• The M protein exhibits more pronounced changes from the ancestral state compared to the F protein.
• Observed variations occur in parallel across different bivalve species, with alanine and serine substitutions having a notable impact.

Conclusions:

• The observed amino acid changes in F and M COI proteins suggest potential functional divergence.
• These differences may influence ATP production and mitochondrial membrane potential, with implications for sperm function.
• Evolutionary forces, including relaxed selection and positive selection, likely contribute to these distinct protein profiles.