PEPTIDE-SPECIFIC ANTIBODIES LOCALIZE THE MAJOR LIPID-BINDING SITES OFTALIN DIMERS TO OPPOSITELY ARRANGED N-TERMINAL 47 KDA SUBDOMAINS

Using ultrastructural analysis and labeling with polyclonal antibodies that recognize peptide sequences specific for phospholipid binding, w e mapped the functional domain structure of intact platelet talin and its proteolytic fragments. The talin dimer, which is crucial for actin and lipid binding, is built of a backbone containing the 200 kDa rod portions, at both ends of which a 47 kDa globular domain is attached. Peptide-specific polyclonal antibodies were raised against three poten tial lipid binding sequences residing within the N-terminal 47 kDa dom ain (i.e. S19, amino acids 21-39; H18, amino acids 287-304; and H17, a mino acids 385-406), Antibodies H17 and H18 localize these lipid bindi ng sequences within the N-terminal 47 kDa globular talin subdomains op posed at the outer 200 kDa rod domains within talin dimers, Hence, we conclude that in its dimeric form, which is used in actin and lipid bi nding, talin is a dumbbell-shaped molecule built of two antiparallel s ubunits. (C) 1998 Federation of European Biochemical Societies.