Figure 2. Multiple sequence alignment of serum albumin proteins from 46 different species (including pigeon seroalbumin, used to root the tree) showing relevant portions of the HSA sequence involved in the aldol condensation. Arginine and lysine are colored blue and pink respectively. Also, the residues involved in the aldol condensation, Lys 199, Arg 218, and Arg 222 (following the HSA numeration) were highlighted. In the internal nodes are highlighted the evolutionary changes (derived from the ancestral reconstruction protocol, see Methods) in positions 199 and 222, respectively. No changes were observed on position 218..