Evolutionary Transformations of Albumin Using the Example of Model Species of Jawless Agnatha and Bony Jawed Fish (Review)

Abstract

Issues of the organization of albumin (a protein belonging to the superfamily of albuminoids) are considered using the example of model representatives of lower aquatic vertebrates: jawless Agnatha (Cyclostomata) and jawed bony lobe-finned (Sarcopterygii) and ray-finned (Actinopterygii: Chondrostei, Holostei, Teleostei) fish. A comparative analysis is carried out of the total length and the length of coding and noncoding sequences of the albumin gene; the number of exons, the length of introns, and the presence of repeated DNA elements in them; and the presence/absence of paralogous genes, their chromosomal affiliation, and the composition of syntenic groups. A comparative analysis of the length of the amino acid sequence, the number of domains, and S–S bonds in the albumin structure is also carried out. The issues of the emergence of the ancestral gene for albuminoids, the “expansion” and “narrowing” of the albuminoid repertoire in different groups of vertebrates, the appearance of a cluster of paralogous genes within a single chromosome in the Sarcopterygii branch and paralogous genes on different chromosomes in the Actinopterygii branch in the representatives of cartilaginous ganoids and teleost fish, the elongation of the gene and protein chain of albumin in the lamprey line, and losses of the albumin gene in the largest groups of teleost fish (Ostariophysi and Acanthopterygii) are discussed. The listed scenarios are considered in light of their consistency with the events of whole genome, local, and segment duplications. The problem of compensating for the functions of the “lost” albumin gene due to multiple osmotically active plasma proteins is discussed using the example of the group of teleost fish.