Role of the beta-strand insert in the central domain of the fibrinogen gamma-module.
The crystal structure of the fibrinogen gamma-module (residues gamma143-411) [Yee, V. C., et al. (1997) Structure 5, 125-138] revealed an unusual feature. Namely, residues gamma381-390 in the functionally important COOH-terminal region form a beta-strand that is inserted into an antiparallel beta-sheet of the central domain (gamma192-286), while the rest (gamma393-411) seems to be flexible. To clarify the structural and functional importance of this beta-strand insert, we analyzed the folding status of the plasmin-derived fibrinogen fragment D(3) and several truncated variants of the gamma-module expressed in Escherichia coli. It was found that D(3), in which most of the COOH-terminal domain of the gamma-module (gamma287-379) is removed proteolytically, retains a gamma374-405 peptide that seems to be associated noncovalently with the bulk of the molecule via its beta-strand insert region. A study of the denaturation-renaturation process of D(3) suggested that without this peptide its truncated gamma-module remains folded but is destabilized. This was confirmed directly with the truncated recombinant variants of the gamma-module, including residues gamma148-392, gamma148-373, and gamma148-286. They all were folded, but those devoid of the beta-strand insert were destabilized. The results indicate that although the beta-strand insert contributes to the stabilization of the gamma-module, it can be removed without destroying the compact structure of the latter. On the basis of this finding and some other observations, we propose a mechanism for the function-related conformational changes in the fibrin(ogen) gamma-modules.
Yakovlev
S
S
Department of Biochemistry, The American Red Cross Holland Laboratory, Rockville, Maryland 20855, USA.
Litvinovich
S
S
Loukinov
D
D
Medved
L
L
D002152:Calorimetry, Differential Scanning; D002850:Chromatography, Gel; D003198:Computer Simulation; D005338:Fibrin Fibrinogen Degradation Products / Q000235:genetics / Q000378:metabolism; D005340:Fibrinogen / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D017510:Protein Folding; D017433:Protein Structure, Secondary / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D017384:Sequence Deletion; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship; D013816:Thermodynamics
D005338:Fibrin Fibrinogen Degradation Products; D010446:Peptide Fragments; D011994:Recombinant Proteins; C015214:fibrinogen D fragment; D005340:Fibrinogen