Computer‐assistant prediction of phospholipid binding sites of caldesmon and calponin

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Abstract
The primary structure of smooth muscle caldesmon and calponin was screened for the presence of amphiphilic α‐helices which can participate in the formation of protein‐lipid contacts. Only one caldesmon segment (residues 645–660) having a predominantly α‐helical structure and high hydrophobic moment satisfies all criteria for a surface‐seeking helix and is predicted to be involved in the caldesmon‐phospholipid interaction. This prediction agrees with experimental results indicating that one of the caldesmon‐phospholipid binding sites is located in the sequence 628–658 [Bogatcheva et al. (1994) FEBS Lett. 342, 176]. Two segments of calponin (residues 45–55 and 85–95) exhibit high hydrophobic moments and the sequence 85–95 is characterized by a high probability of α‐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.