Taxonomic distribution of proteins containing ALBUMIN domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing ALBUMIN domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

Structure of serum albumin.

Carter DC, Ho JX
Adv Protein Chem. 1994; 45: 153-203

Characterization, primary structure, and evolution of lamprey plasma albumin.

Gray JE, Doolittle RF
Protein Sci. 1992; 1: 289-302

The most abundant protein found in blood plasma from the sea lamprey (Petromyzon marinus) has the hallmarks of a plasma albumin: namely, high abundance, solubility in distilled water, a small number of tryptophans, and a high content of cysteines and charged residues. As in other vertebrate albumins, not all the cysteines are disulfide bonded. An unusual feature of this protein is its molecular weight of 175,000, roughly 2.5 times the size of other vertebrate albumins. Its amino acid sequence, deduced from a series of overlapping cDNA clones, can be aligned with other members of the gene family including plasma albumin, alpha-fetoprotein, and vitamin-D binding protein, confirming that it is indeed an oversized albumin. An unusual feature of the sequence is a 28-amino acid stretch consisting of a serine-threonine repeat with the general motif (STTT). Lamprey albumin contains a 23-amino acid putative signal peptide and a 6-residue putative propeptide, which, when cleaved, yield a mature protein of 1,394 amino acids with a calculated molecular weight of 157,000. The sequence also includes nine potential N-linked glycosylation sites (Asn-X-Ser/Thr), consistent with observation that lamprey albumin is a glycoprotein. If all the potential glycosylation sites were occupied by clusters of 2,000 molecular weight each, the total molecular weight would be 175,000. Like other members of the gene family, lamprey albumin is composed of a series of 190-amino acid repeats, there being seven such domains all together. Quantitative amino acid sequence comparisons of lamprey albumin with the other members of the gene family indicate that it diverged from an ancestral albumin prior to the gene duplications leading to this diverse group. This notion is confirmed by the pattern of amino acid insertions and deletions observed in a consideration of all domains that compose this family. Furthermore, it suggests that the invention of albumin antedates the vertebrate radiation.

Evolution of the albumin: alpha-fetoprotein ancestral gene from the amplification of a 27 nucleotide sequence.

Alexander F, Young PR, Tilghman SM
J Mol Biol. 1984; 173: 159-73

The genes for alpha-fetoprotein and albumin arose by duplication of an ancestral gene that contained three genetic domains. These domains were generated by the triplication of a primordial genetic domain composed of five exons or subdomains. That the primordial domain itself arose by amplification of a simpler sequence is suggested by nucleotide sequence homologies among the subdomains of the mouse alpha-fetoprotein gene. A detailed analysis of these homologies reveals that each of the five subdomain families contains remnants of a 27-base-long repeat from which the entire alpha-fetoprotein coding sequence has been assembled. A consensus sequence for the 27 nucleotide repeat is derived, and the positions of the repeats within each subdomain are described. A model is proposed for the evolution of the primordial domain by the amplification and divergence of the 27 base-pair sequence, along with the condensation of the repeats into subdomains separated by intervening sequences. It is postulated that the role of intervening sequences may be to limit sequence amplification in genes such as alpha-fetoprotein and albumin whose protein products cannot tolerate size variation.

Intragenic amplification and divergence in the mouse alpha-fetoprotein gene.

Eiferman FA, Young PR, Scott RW, Tilghman SM
Nature. 1981; 294: 713-8

The DNA sequences of the 14 exon junctions in the murine alpha-fetoprotein gene were determined using cloned genomic DNA. When these exons were examined with respect to the polypeptide segments they encoded, a direct correspondence between a threefold repeat of four exons and three protein domains was observed. Nucleotide sequence comparisons among the four exons of each domain were used to deduce the likely structure of the primordial domain, and the order and mechanism of its triplication to form the tripartite ancestral gene from which both alpha-fetoprotein and serum albumin arose. Sequence homologies among the four exons that constitute a single domain also suggest that they were derived, at least in part, from a common sequence which underwent successive amplification and divergence.