AN INTRAMOLECULAR DISULFIDE BOND IS ESSENTIAL FOR ANNEXIN I-MEDIATED LIPOSOME AGGREGATION

Dithiothreitol (DTT) inhibits the annexin I-mediated aggregation of ph osphatidylserine (PS) liposomes, but has no effect on its binding to P S vesicles. Non-reducing SDS gel analysis indicates that intermolecula r disulfide bonds between annexin I molecules are not involved in lipo some aggregation. However, DTT causes changes in protein conformation of annexin I as monitored by hydrophobic fluorescent dye treatment. Th e results suggest that the reduction of the intramolecular disulfide b ond leads to inhibition of annexin I-mediated liposome aggregation via protein conformational changes.