Figure 1.

Schematic diagram of the 45 nm long fibrin(ogen) molecule includes information that helps to frame the issue of the location of the C-terminal region of the γ chain. End-to-middle assembly of fibrin molecules to form half-staggered double-stranded fibrils is shown, illustrating the polymerization site interaction (Da:E_A) that governs the assembly process. The crosslinking arrangement of γ_XL sites of γ chains in transverse or end-to-end orientations is shown, as is the C-terminal sequence of the γ chain from γ398 to the C-terminus at γ411. The terminal portion of the γ chain emerges 3.5 nm from the distal end of each molecule (27). The positioning of end-to-end-crosslinked γ chains has been adjusted from the originally proposed location at the extreme ends of the D domain (DD-long; ref. 20) to take into account recent data indicating that their location at the D:D site is not a realistic possibility (1, 21, 25, 27).