Acid induced equilibrium unfolding of annexin V wild type shows two intermediate states

Annexin V is an alpha-helical protein which shows anticoagulatory and antiinflammatory activity. It is supposed to be involved in membrane fusion and exocytosis. In this study acid-induced equilibrium unfolding of the human annexin V is investigated by fluorescence and circular dichroism spectroscopy. The spectroscopic data indicate that at least two intermediate states are involved in unfolding. One of the proposed intermediate states exhibits properties similar to those observed with annexin V wild type saturated with calcium, another may be regarded as 'molten globule'.