ACTIN INTERACTION WITH PURIFIED DYSTROPHIN FROM ELECTRIC ORGAN OF TORPEDO-MARMORATA - POSSIBLE RESEMBLANCE WITH FILAMIN ACTIN INTERFACE

We have purified dystrophin from Torpedo marmorata electric tissue by means of alkaline extraction in conjunction with an affinity chromatog raphy column using anti-peptide antibodies. Using solution (cosediment ation) and solid phase experiments (sedimentation with Sepharose filam entous actin and ELISA), we have demonstrated that purified dystrophin is able to bind filamentous and monomeric actin. Using ELISA coupled with biotin labelled peptides and taking advantage of strong affinity binding of streptavidin-biotin complex, we have identified two exposed sequences of the actin molecule implicated in dystrophin binding: fra gment 40-113, further restricted to peptide 75-106 and peptide 360-372 . In a previous study, we have shown that fragment 40-113 displays bin ding site(s) for filamin but probably not for alpha-actinin. Moreover, we have recently reported that alpha-actinin and filamin display dive rgent behaviours towards conformational changes of actin. In this stud y, we have demonstrated that, similarly to filamin, dystrophin binding is insensitive to the locking of actin in a monomeric conformation. T aken together, these results lead us to favour the idea that dystrophi n could share properties in common with filamin in its binding of acti n.