... lysine (Lys), isoleucine (Ile), asparagine (Asn), and tyrosine (Tyr) are used less frequently as the species' coding sequence GC3 content increases. (b) AAs alanine (Ala), glycine (Gly), ... protein sequences, especially atfunctionally unconstrained positions. For example, the frequencies of both lysine and arginine are highly (but oppo-sitely) correlated with GC content, and lysine ... supporting evidence in the form of similarity to known or predicted proteins (BLASTXcutoff 1 × e-8) and retained only the polypeptide aligned por-tion of the nucleotide sequence. About 75% of the...