Evolution of the albumin protein family in reptiles.

The albumin family of proteins consists of vitamin-D binding protein/group-specific component (GC), serum albumin (ALB), alpha-fetoprotein (AFP), and afamin (AFM), which are responsible for transporting many ligands throughout the body. The albumin family proteins are physiologically and medically important, but our understanding of their functions and applications is hindered by the dearth of information regarding these proteins' evolutionary relationships and functions in non-mammalian lineages. In this study we investigate the evolution of the albumin family proteins in reptiles, using bioinformatic methods to survey available reptile genomes and transcriptomes for albumin family proteins and phylogenetically characterize their relationships. We reinforce the established evolutionary relationships among the albumin protein family in reptiles, however, they are variable in their number of domains, overall genetic sequence, and synteny. We find a novel absence of the physiologically important ALB in squamates and identify two distinct lineages of AFP, one in mammals and another in reptiles. Our study provides a comparative genomic framework for further studies identifying lineage-specific gene expansions that may compensate for the lack of serum albumin in squamates.