Fig. 4.

Genomic and molecular markers of horizontal gene transfer. Where available, codon usage for conserved Ser56, whole-genome sequence (WGS) GC%, and the ratio of serpin gene sequence GC% to WGS GC% are mapped to prokaryotic serpins belonging to Groups S–U. There are no systematic anomalous ratios in serpin gene GC% to WGS GC% over a wide range of whole-genome sequence GC contents (<30% to >70%). Likewise, there is no systematic evidence that Groups S–U were acquired from chordates from the pseudoconserved Ser56 codon usage in prokaryotes.