Urea-induced sequential unfolding of fibronectin: a fluorescence spectroscopy and circular dichroism study.


Fibronectin (FN) is an extracellular matrix (ECM) protein found soluble in corporal fluids or as an insoluble fibrillar component incorporated in the ECM. This phenomenon implicates structural changes that expose FN binding sites and activate the protein to promote intermolecular interactions with other FN. We have investigated, using fluorescence and circular dichroism spectroscopy, the unfolding process of human fibronectin induced by urea in different ionic strength conditions. At any ionic strength, the equilibrium unfolding data are well described by a four-state equilibrium model N <= => I(1) <= =>I(2) <= => U. Fitting this model to experimental values, we have determined the free energy change for the different steps. We found that the N <= => I(1) transition corresponds to a free energy of 10.5 +/- 0.4 kcal/mol. Comparable values of free energy change are generally associated with a partial unfolding of the type III domain. For the I(1) <= => I(2) transition, the free energy change is 7.6 +/- 0.4 kcal/mol at low ionic strength but is twice as low at high ionic strength. This result is consistent with observations indicating that the complete unfolding of the type III domain from partially unfolded forms necessitates about 5 kcal/mol. The third step, I(2) <= => U, which leads to the complete unfolding of fibronectin, corresponds to a free energy change of 14.4 +/- 0.9 kcal/mol at low ionic strength whereas this energy is again twice as low under high ionic strength conditions. This hierarchical unfolding of fibronectin, as well as the stability of the different intermediates controlled by ionic strength demonstrated here, could be important for the understanding of activation of the matrix assembly. Study holds ProTherm entries: 16863, 16864, 16865, 16866, 16867, 16868, 16869, 16870, 16871, 16872, 16873, 16874, 16875, 16876, 16877 Extra Details: Transition 1. Experiment was done in pure water, 18 M ohm. structural changes; binding sites; intermolecular interactions; partial unfolding; ionic strength

Submission Details


Submitter: Connie Wang

Submission Date: April 24, 2018, 8:48 p.m.

Version: 1

Publication Details
Patel S;Chaffotte AF;Goubard F;Pauthe E,Biochemistry (2004) Urea-induced sequential unfolding of fibronectin: a fluorescence spectroscopy and circular dichroism study. PMID:14769050
Additional Information

Structure view and single mutant data analysis

Study data

No weblogo for data of varying length.
Colors: D E R H K S T N Q A V I L M F Y W C G P

Data Distribution

Studies with similar sequences (approximate matches)

Correlation with other assays (exact sequence matches)

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
100.0 Fibronectin P02751 FINC_HUMAN
96.8 Fibronectin P07589 FINC_BOVIN
94.0 Fibronectin Q28275 FINC_CANLF
92.1 Fibronectin Q28377 FINC_HORSE
90.9 Fibronectin Q91400 FINC_NOTVI