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.
Laboratory of Biophysical Chemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, 50 Center Drive, Bethesda, Maryland 20892, USA.
Robert A
RA
Burton
Galina
G
Tsurupa
Leonid
L
Medved
Nico
N
Tjandra
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