ANNEXIN-I, ANNEXIN-II AND ANNEXIN-III ARE SPECIFIC CHOLINE BINDING-PROTEINS

We have isolated choline binding proteins from the plasma membrane fra ction of human lung epithelium-derived cell line (A549) by means of de tergent solubilization, anion exchange and affinity chromatography. On e of the affinity purified proteins had a specific choline binding act ivity of 44-57 rho mol/mg, representing a two to three hundredfold enr ichment relative to the specific activity of freshly prepared plasma m embranes. The purified protein has a molecular mass of 38 kDa by SDS P AGE analysis and was identified as annexin II by N-terminal microseque ncing. Annexin II, however, had not previously been known for choline binding activity. We therefore prepared a mixture of authentic annexin s (I-V) from A549 cells. The mixture had a choline binding activity of 15 to 18 rho mol/mg. The annexin mixture was subsequently affinity ch romatographed on the choline-conjugated Sepharose 6B column. Analyses by SDS PAGE and immunoblot revealed that annexins I, II, and III are b ound to the choline column while annexins IV and V did not. These resu lts indicate that some of the annexins have specific choline binding a ctivities.