Enzymic and immunochemical properties of lysozyme: IV. Demonstration of conformational differences between α-lactalbumin and lysozyme

Abstract

Several chemical as well as immunochemical methods have been utilized to determine conformational differences between lysozyme and α-lactalbumin. Of these, the reactivity of free amino groups with trinitrobenzene sulfonic acid and the reactivity of tyrosine residues with tetranitromethane showed small differences in accessibility. Immunochemical studies indicated lack of cross reaction between lysozyme and anti α-lactalbumin and between α-lactalbumin and anti-lysozyme. By far, the reactivity of the disulfide bonds to reduction with β-mercaptoethanol in absence and presence of guanidine revealed considerable differences between lysozyme and α-lactalbumin. Whereas, 2.6 disulfide bonds were reducible in α-lactalbumin, none was reduced in lysozyme. The binding of sodium dodecyl sulfate to lysozyme produced a relaxed conformation while with α-lactalbumin a constrained conformation resulted. The present findings lead to the conclusion that conformational differences between lysozyme and α-lactalbumin are appreciable.