Subunit conformation of yeast alcohol dehydrogenase.

The primary structure of yeast alcohol dehydrogenase has been compared to the known tertiary structure of the corresponding horse liver enzyme after proper alignment of the two proteins. Possible influences on the subunit conformations of all amino acid exchanges, which affect 75% of the positions, were examined from interactions in the x-ray model of the horse enzyme. In spite of the differences, 90 of 93 strictly internal residues are similar, 18 space-restricted glycine residues are conserved, 16 structurally compensated exchanges occur, all functionally essential residues are similar or identical, and 41 gaps in either sequence may be accommodated in the model. These results show that the general subunit conformations and enzymatic mechanisms of the two enzymes are largely identical. Four surface areas are changed, affecting a region with differing charges, a noncommon loop, a structure around the second zinc atom, and residues at the main dimer interface. Although the subunit interactions in the yeast enzyme cannot be determined, the surface changes probably correlate with differences in quaternary structure between the proteins.