1H NMR-based determination of the three-dimensional structure of the human plasma fibronectin fragment containing inter-chain disulfide bonds.
Human plasma fibronectin is a plasma glycoprotein that plays an important role in many biological processes. It consists of two identical 230-250-kDa subunits that are joined by two disulfide bonds near their carboxyl termini. Each subunit contains various binding domains composed of three types of homologous repeats. Recent work has determined the three-dimensional structures of various repeat fragments, but little is known about the three-dimensional structure of the carboxyl-terminal region. A recent NMR study of a plasmin-digested carboxyl-terminal inter-chain disulfide-linked heptapeptide dimer has proposed that the two subunits are arranged in an antiparallel fashion (An et al. (1992) Biochemistry 31, 9927-9933). We have now determined the three-dimensional structure for a substantial portion of a trypsin-digested interchain disulfide-linked 52-residue (6 kDa) fragment of the carboxyl-terminal of human plasma fibronectin (which includes the above-mentioned heptapeptide dimer) using two-dimensional NMR methods and a new strategy for NMR-based protein structure determination. The NMR data requires that the two chains in the dimer be linked in a symmetric, antiparallel arrangement. The resulting monomer conformation consists of two twisted or coiled segments, Thr3-Asn6 and Ile9-Phe12, connected by the Cys7-Pro8 residues in extended conformations, with the two monomer chains cross-linked at residues Cys7 and Cys11. The conformation of the heptapeptide dimer region differs substantially from the conformation proposed by An et al.
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Center for Pharmaceutical Biotechnology, University of Illinois, Chicago 60680.
Lai
C S
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Wolff
C E
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Nettesheim
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D
Sherman
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Johnson
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ME
D000595:Amino Acid Sequence; D003198:Computer Simulation; D004220:Disulfides / Q000737:chemistry*; D005353:Fibronectins / Q000097:blood / Q000737:chemistry*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D011487:Protein Conformation
D004220:Disulfides; D005353:Fibronectins; D010446:Peptide Fragments