ADP - Induced Platelet Aggregation Depends on the Conformation or Availability of the Terminal Gamma Chain Sequence of Fib rinogen

Fibrinogen Paris I contains a mutant “y chain that is longer than the normal chain. resulting in altered fubrin polymerization and cross-linking. Because these functions involve the carboxy-terminal region of the ‘y chain, we decided to determine whether fibrinogen Paris I or the isolated Paris I “1 chain supports normal ADP-induced platelet aggregation, a function that requires the ultimate 1 2 residues of the normal ‘y chain (400 through 41 1 ). Aggregation of ADPstimulated normal platelets was defective with fibrinogen Paris I and markedly depressed with the ‘y Paris I chain. These findings prompted us to characterize the carboxyterminal structure of the region of the ‘y Paris I chain responsible for this activity. The carboxy-terminal cyanogen bromide (CNBr) peptide of the normal ‘y chain (385 through 41 1 ) or that from ‘y Paris I was isolated by differential adsorption to triethylene-tetramine resin or by reverse-phase high-performance liquid chromatography (HPLC). The CNBr peptide from the Paris I ‘y chain was