ISOLATION, CHARACTERIZATION AND LOCALIZATION OF ANNEXIN-V FROM CHICKEN LIVER

Annexin V has been purified from chicken liver; 40 mg of annexin V was obtained per kg of tissue. In contrast with mammalian liver, very little annexin VI was obtained. Surprisingly, chicken liver annexin V resembles mammalian annexin IV in its M(r) (32 500) and its isoelectric point (5.6), but amino-acid-sequence analysis demonstrates identity with chicken annexin V (anchorin CII). It binds to phospholipids in a Ca2+-dependent manner with free-Ca2+ concentrations for half-maximal binding to phosphatidylserine and phosphatidic acid of 10 muM; phosphatidylethanolamine of 32 muM and phosphatidylinositol of 90 muM. No binding to phosphatidylcholine was observed at Ca2+ concentrations up to 300 muM. In isolated liver membranes a significant proportion of annexin V was not extractable with EGTA but could only be extracted with Triton X-100, suggesting the existence of a tightly membrane-associated form of annexin V. A specific antiserum to chicken annexin V was used to localize the protein in adult and embryonic chicken liver. In the adult, annexin V was highly concentrated in epithelial cells lining the bile ducts, and along the bile canaliculi. In embryonic liver, strong staining of the bile-duct epithelial cells was again evident, and in addition, endothelial cells were strongly immunoreactive.