¹H NMR Sequential Assignments and Secondary Structure Analysis of Human Fibrinogen C-Chain C-Terminal Residues 385–411

The human fibrinogen γ-chain, C-terminal fragment, residues 385–411, i.e., KIIPFNRLTI-GEGQQHHLGGAKQAGDV, contains two biologically important functional domains: (1) fibrinogen γ-chain polymerization center and (2) platelet receptor recognition domain. This peptide was isolated from cyanogen bromide degraded human fibrinogen and was investigated by ¹H NMR (500 MHz) spectroscopy. Sequence-specific assignments of NMR resonances were obtained for backbone and side-chain protons via analysis of 2D NMR COSY, double quantum filtered COSY, HOHAHA, and NOESY spectra. The N-terminal segment from residues 385–403 seems to adopt a relatively fixed solution conformation. Strong sequential αCH-NH NOESY connectivities and a continuous run of NH-NH NOESY connectivities and several long-lived backbone NH protons strongly suggest the presence of multiple-turn or helix-like structure for residues 390 to about 402. The conformation of residues 403–411 seems to be much less constrained as evidenced by the presence of weaker and sequential aCH-NH NOEs, the absence of sequential NH-NH NOEs, and the lack of longer lived amides. Chemical shifts of resonances from backbone and side-chain protons of the C-terminal dodecapeptide, residues 400–411, differ significantly from those of the parent chain, suggesting that some preferred C-terminal conformation does exist.