Comparison of molecular clocks of Nox domains.(A) Amino acid sequences were trimmed to the length of human Nox2 as Nox domains, and the numbers of amino acid substitutions per site relative to the human isolog were counted. Each data point represents amino acid substitution rates per site per 109 years for a given isolog (see Additional file 3). (B) Each data point represents amino acid substitution rates of regulatory subunits per site per 109 years. Asterisks indicate significance: p < 0.001 (*) or p < 0.002 (**).