COMPUTER-ASSISTANT PREDICTION OF PHOSPHOLIPID-BINDING SITES OF CALDESMON AND CALPONIN

The primary structure of smooth muscle caldesmon and calponin was scre ened for the presence of amphiphilic alpha-helices which can participa te in the formation of protein-lipid contacts, Only one caldesmon segm ent (residues 645-660) having a predominantly alpha-helical structure and high hydrophobic moment satisfies all criteria for a surface-seeki ng helix and is predicted to be involved in the caldesmon-phospholipid interaction. This prediction agrees with experimental results indicat ing that one of the caldesmon-phospholipid binding sites is located in the sequence 628-658 [Bogatcheva et al, (1994) FEES Lett, 342, 176], Two segments of calponin (residues 45-55 and 85-95) exhibit high hydro phobic moments and the sequence 85-95 is characterized by a high proba bility of alpha-helix formation, This may suggest that at least one of these segments could facilitate the calponin-phospholipid interaction and that calponin, as with many other actin binding proteins, is able to interact with membranes.