We have prepared interferon-gamma (IFN-gamma) analogs to study the structural role of particular amino acids in relation to their effects on antiviral activity. Three IFN-gamma analogs were prepared on the basis of predicted secondary structure. In two of the analogs, [Gln25]IFN-gamma and [Thr45]IFN-gamma, changes were made at residue 25 (Asn to Gln) and at residue 45 (Met to Thr), respectively. [Gln25Lys78]IFN-gamma had two changes, at residue 25 (Asn to Gln) and residue 78 (Asn to Lys). Another analog, [Cys-Tyr-Cys]IFN-gamma, incorporated Cys-Tyr-Cys at the amino terminus. Comparison of the structure and activity of these analogs with that of the natural sequence protein suggested that residues 25 and 78 are at the protein surface and play an important role in antiviral activity. The residue at position 45 was found to be important for maintaining the protein structure, as assessed by circular dichroism spectroscopy. The addition of Cys-Tyr-Cys resulted in a small perturbation of protein structure and a small decrease in antiviral activity.

Rat liver glyoxalase II has been purified to homogeneity by a rapid, two-step procedure involving affinity chromatography on S-carbobenzoxyglutathione coupled to Sepharose 4B. The purified enzyme gives a major band corresponding to 30,000 daltons (monomer) and a minor band corresponding to 120,000 daltons (tetramer) with sodium dodecylsulfate polyacrylamide gel electrophoresis. Evidence is given for the interconversion of the monomer and tetramer forms of glyoxalase II via the dimer and the trimer.