Identification of an ordered compact structure within the recombinant bovine fibrinogen alphaC-domain fragment by NMR.
The NMR solution structure of the bovine fibrinogen alphaC-domain fragment, including residues Aalpha374-538, reveals a type-I' beta-hairpin, restricted at the base by a C423-C453 disulfide linkage and a short turn preceding C423. Although both faces of the hairpin are formed mainly by hydrophilic residues, one of them is uncharged while the other has a characteristic pattern of charged residues which are highly conserved among vertebrate species. Chemical shift indexing and relaxation data indicate the presence of a collapsed hydrophobic region next to the hairpin that includes approximately 30 residues with slower concerted motion and higher content of nonpolar residues and, according to a previous study (Tsurupa, G., Tsonev, L., and Medved, L. (2002) Biochemistry 41, 6449-6459), may cooperate with the hairpin to form a compact cooperative unit (domain). Structure and relaxation data show that the region between C423 and C453 is populated by both random coil and beta-structure, suggesting that the cooperative structure in the isolated alphaC-domain is intrinsically unstable. This observation is in agreement with a very low energy of stabilization of the Aalpha374-538 fragment determined in unfolding experiments. The low stability of the alphaC-domain suggests a possible explanation for the previously observed intra- and intermolecular interactions of these domains in fibrinogen and fibrin.
Burton
Robert A
RA
Laboratory of Biophysical Chemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, 50 Center Drive, Bethesda, Maryland 20892, USA.
Tsurupa
Galina
G
Medved
Leonid
L
Tjandra
Nico
N
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D005340:Fibrinogen / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry*; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry; D016415:Sequence Alignment
D010446:Peptide Fragments; D011994:Recombinant Proteins; C098000:fibrinogen alphaC; D005340:Fibrinogen