THE 2 POLYPEPTIDE-CHAINS IN FIBRONECTIN ARE JOINED IN ANTIPARALLEL FASHION - NMR STRUCTURAL CHARACTERIZATION

The fibronectin C-terminal interchain disulfide-linked heptapeptide dimer (Val-Asn-Cys-Pro-Ile-Glu-Cys)2 has been investigated via H-1 NMR spectroscopy in both water and dimethyl sulfoxide (DMSO) solutions. Proton Overhauser experiments in DMSO indicate unambiguously that the two fibronectin polypeptide chains are linked head-to-tail (N-terminus to C-terminus), in an antiparallel fashion. It is found that the structure of the peptide is extended. From the H-1 NMR interproton distance and angle constraints, the preferred mean (time-averaged) conformations in both H2O and DMSO were derived using distance geometry and molecular mechanics algorithms. The two conformations, although significantly dissimilar, exhibit the common feature of a structurally parallel (as opposed to chemically antiparallel) fibronectin alpha/beta chain array.