title: Cystatin domains in alpha-2-HS-glycoprotein and fetuin.
abstract: We have found that chain A of alpha-2-HS-glycoprotein contains two cystatin domains that show closest similarity to those of kininogen. Most likely, the two proteins diverged after the primary duplication of a single cystatin domain as the two cystatin domains of alpha-2-HS-glycoprotein are more similar, especially in disulfide bonding, to the corresponding domains of kininogen than to each other. We also propose that the carboxyl-terminal (non-cystatin) parts of kininogen and alpha-2-HS-glycoprotein contain homologous segments. We suggest that alpha-2-HS-glycoprotein may act as an inhibitor of the cysteine proteinases responsible for bone resorption. We have also found that fetuin is closely related to alpha-2-HS-glycoprotein.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001798:Blood Proteins / Q000235:genetics*; D015853:Cysteine Proteinase Inhibitors; D006801:Humans; D007704:Kininogens / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D011480:Protease Inhibitors / Q000235:genetics*; D013045:Species Specificity; D060749:alpha-2-HS-Glycoprotein; D000509:alpha-Fetoproteins / Q000235:genetics*
chemical_list: C556354:AHSG protein, human; D001798:Blood Proteins; D015853:Cysteine Proteinase Inhibitors; D007704:Kininogens; D011480:Protease Inhibitors; D060749:alpha-2-HS-Glycoprotein; D000509:alpha-Fetoproteins