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Thermal denaturation of a recombinant mouse amelogenin: Circular dichroism and differential scanning calorimetric studies
Author(s) -
Oobatake Motohisa,
Yamasaki Tomoko,
Simmer James P.,
Renugopalakrishnan V.
Publication year - 2005
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.20747
Subject(s) - circular dichroism , random coil , differential scanning calorimetry , chemistry , protein secondary structure , globular protein , molten globule , denaturation (fissile materials) , fluorescence , crystallography , analytical chemistry (journal) , chromatography , nuclear chemistry , biochemistry , physics , quantum mechanics , thermodynamics
Conformational analyses of a recombinant mouse tooth enamel amelogenin (rM179) were performed using circular dichroism (CD), fluorescence, differential scanning calorimetry, and sedimentation equilibrium studies. The results show that the far‐UV CD spectra of rM179 at acidic pH and 10°C are different from the spectra of random coil in 6 M GdnHCl. A near‐UV CD spectrum of rM179 at 10°C is similar to that of rM179 in 6 M GdnHCl, which indicates that aromatic residues of native structure are exposed to solvent and rotate freely. Far‐UV CD values of rM179 at 80°C are different from that of random‐coil structure in 6 M GdnHCl, which suggests that rM179 at 80°C has specific secondary structures. A gradual thermal transition was observed by far‐UV CD, which is interpreted as a weak cooperative transition from specific secondary structures to other specific secondary structures. The fluorescence emission maximum for the spectrum due to Trp residues in rM179 at 10°C shows the same fluorescence emission maximum as rM179 in 6 M GdnHCl and amino acid Trp, which indicates that the three Trp in rM179 are exposed to solvent. Deconvolution of differential scanning calorimetry curve gives the population of three states (A, I, and C states). These results indicate that three states (A, I, and C) have specific secondary structures, in which hydrophobic and Trp residues are exposed to the solvent. The thermodynamic characteristics of rM179 are unique and different from a typical globular protein, proline‐rich peptides, and a molten globule state. Proteins 2006. © 2005 Wiley‐Liss, Inc.