Structural properties of recombinant ovalbumin and its transformation intoa thermostabilized form by alkaline treatment

The recombinant ovalbumin produced in Escherichia coli was purified from th e cytoplasmic fraction and analyzed for its chemical and conformational pro perties. The recombinant ovalbumin displayed almost exactly the same circul ar dichroism and intrinsic tryptophan fluorescence spectra as egg white ova lbumin, As in the egg white protein, four cysteine sulfhydryls and one cyst ine disulfide were contained in the recombinant protein, according to the r esults of amino acid analyses; the disulfide bond was found by a peptide ma pping analysis to correspond to the native cystine, Cys(73)-Cys(120). Accor ding to a gel electrophoresis analysis, the presence of the disulfide bond was accounted for by specific oxidation of the corresponding cysteine resid ues during purification of the cytoplasmic protein, Unlike the identity in the conformational and peptide structures, none of the post-translational m odifications (N-terminal acetylation, phosphorylation, and glycosylation) t hat are known with egg white ovalbumin were detected in the recombinant pro tein. The recombinant ovalbumin was transformed into a thermostabilized for m in a similar manner to the transformation of egg white protein into S-ova lbumin; alkaline treatment increased the temperature for thermostability by 8.7 degrees C. These data strongly suggest that the post-translational mod ifications of ovalbumin are not related to the formation mechanism for S-ov albumin.