Structural and functional comparison of anchorin CII (cartilage annexin V) and muscle annexin V.

Annexin V has been isolated from chicken muscle and cartilage either by EDTA extraction or by plasma membrane purification and solubilization with detergent to obtain the hydrophilic and hydrophobic variants. The hydrophobic variant of the cartilage annexin V associated with phosphatidylserine-containing liposomes in a Ca(2+)-independent manner, whereas the EDTA-extracted molecule required Ca2+ for association with the liposomes. The collagen-binding assay used is based on the principle of a cell attachment assay using mildly pepsinized collagen type II or intact collagen type I as the solid-phase substrate. Soluble intact collagen type I or II was added as competitive inhibitor. The lipophilic and the EDTA-extracted anchorins CII from cartilage were inhibited to the same extent by collagen type II on pepsinized collagen type II as the solid-phase substrate. The EDTA-extracted muscle annexin V exhibited a fivefold lower affinity to collagen type II than its counterpart from cartilage. Peptide mapping studies and amino acid sequencing of selected peptides from the hydrophobic cartilage annexin V and the hydrophilic cartilage and muscle annexin V revealed 100% identity to the established chicken annexin V protein sequence in the corresponding amino acids 7-29 and 118-126. These results indicate that annexin V may occur in multiple pools within one cell type and/or tissue and that its biological function may depend on the subcellular distribution as well as the microenvironment in the tissue.