Maximum likelihood approach suggests positive selection in platelet integrin αIIbβ3 in mammalian species.

Platelet integrin αIIbβ3 is crucial for platelet aggregation. Although structural and functional characteristics of this protein have been extensively studied, the evolutionary pattern studies of this protein complex in mammals are scarce. Here, we addressed this question using maximum likelihood approaches to identify codons that are evolving under positive selection. Likelihood of positive selection was estimated using CODEML implemented in PAML software applied to integrin αIIbβ3 derived from nucleotide sequences of 10 different mammalian species. Four codons in mature αIIb-subunit (corresponding to residues 150, 184, 193, and 370) and three codons in mature β3-subunit (corresponding to residues 129, 440, and 444) showed signs of positive selection with posterior probabilities over 95%. The different amino acids observed for each of the positively selected residues detected showed different physicochemical properties. These results open new research avenues to understand the physiological importance of specific residues and should allow for a better understanding of the function and the different interactions of each residue within the mature protein.