This entry represents the alpha/beta/alpha domain found in class II aldolases and adducin, usually at the N-terminus. These proteins form part of a family that includes: rhamnulose-1-phosphate aldolase , L-fuculose phosphate aldolase [8515438, 8676381] that is involved in the third step in fucose metabolism, L-ribulose- 5-phosphate 4-epimerase involved in the third step of L-arabinose catabolism, a probable sugar isomerase SgbE, hypothetical proteins and the metazoan adducins which have not been ascribed any enzymatic function but which play a role in cell membrane cytoskeleton organisation.
Adducins are members of the Ig superfamily and encode cell surface sialoglycoproteins expressed by cytokine-activated endothelium. This type I membrane protein mediates leukocyte-endothelial cell adhesion and signal transduction, and may play a role in the development of artherosclerosis and rheumatoid arthritis. Adducin is a cell-membrane skeletal protein that was first purified from human erythrocytes and subsequently isolated from bovine brain membranes. Isoforms of this protein have been detected in lung, kidney, testes and liver. Erythrocyte adducin is a 200-kDa heterodimer protein, composed of alpha and beta subunits, present at about 30,000 copies per cell. It binds with high affinity to Ca(2+)/calmodulin and is a substrate for protein kinases A and C. Both alpha-adducin and beta-adducin show alternative splicing. Thus, there may be several different heterodimeric or homodimeric forms of adducin, each with a different functional specificity. It is thought to play a role in assembly of the spectrin-actin lattice that underlies the plasma membrane . Missense mutations in both the alpha- and beta-adducin genes that alter amino acids that are normally phosphorylated have been associated with the regulation of blood pressure in the Milan hypertensive strain (MHS) of rats. Gamma adducin was isolated from human foetal brain . It shows a high degree of similarity to the alpha and beta adducins.