Thermal unfolding of the tryptic fragment of the membrane-bound protein, cytochrome b5, which contains the residues 1-90, was investigated by scanning calorimetry, circular dichroism and absorption spectroscopy. The fragment undergoes a reversible two-state transition at about 70 degrees C (neutral pH). The fragment exhibits all the thermodynamic properties of small globular proteins with respect to heat capacity and transitional changes of enthalpy, Gibbs energy and heat capacity. The heat capacity change at unfolding fits into the correlation with the specific amount of nonpolar contacts, which has been found to be valid for small globular proteins (Privalov, P.L. and Khechinashvili, N.N. (1974) J. Mol. Biol. 86, 665-684). The relatively low stabilization energy of the cytochrome b5 fragment (delta trsG25 degrees C = 25 kJ/mol) is discussed in terms of the functional requirements of electron-transfer proteins. Study holds ProTherm entries: 11523, 11524 Extra Details: fragment contains the residues 1-90 membrane-bound protein; two-state transition; nonpolar contacts;,electron-transfer proteins
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:42 p.m.
|Number of data points||3|
|Proteins||Cytochrome b5 ; Cytochrome b5|
|Assays/Quantities/Protocols||Experimental Assay: dCp ; Experimental Assay: Tm ; Experimental Assay: dG|
|Libraries||Mutations for sequence DKDVKYYTLEEIKKHNHSKSTWLILHHKVYDLTKFLEEHPGGEEVLREQAGGDATENFEDVGHSTDARELSKTFIIGELHPDDRSKLSKPMETL|