The following serum transport proteins are known to be evolutionary related
Albumin (ALB), the main protein of plasma. It binds water, cations such as
Ca++, Na+, K+, fatty acids, hormones, bilirubin and drugs. Its main
function is the regulation of the colloidal osmotic pressure of blood.
α-fetoprotein (AFP) (α-fetoglobulin). AFP is a fetal plasma protein
which also binds various cations, fatty acids and bilirubin.
Vitamin D-binding protein (VDB), also known as group-specific component or
Gc-globulin. VDB binds to vitamin D and its metabolites as well as fatty
Afamin (or α-albumin), a protein whose biochemical role is not yet
Structurally, these proteins consist of two to seven homologous domains of
about 190 amino acids. Each domain, consisting of 10 α-helices, is formed
by two smaller subdomains and contains five or six internal disulfide bonds as
shown in the following schematic representation .
'C': conserved cysteine involved in a disulfide bond.
'*': position of the pattern.
The signature pattern we derived is based on three conserved cysteines at the
end of the domain. We built it in such a way that it can detect all 3 repeats
in albumin and human afamin, the first two in AFP and the first one in VDB and
rat afamin. We also developed a profile, which covers the entire albumin
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