Protein structures are stabilized by hydrophobic and van der Waals forces, and by hydrogen bonds. The relation between these ther-modynamic quantities and the actual three-dimensional structure of proteins can not be calculated precisely. However, certain empirical relations have been discovered. Hydrophobic energy is gained by the reduction of surface in contact with water1. For monomeric proteins, the area of the surface accessible to solvent, and of that buried in the interior, is a simple function of molecular weight. Proteins with different shapes and secondary structures, but of the same molecular weight, have the same accessible surface area2-5. It has been argued that there is no similar relationship for large oligomeric proteins6. In this paper we show that the surface areas of oligomeric proteins, and the areas of the surface buried within them, are directly related to relative molecular mass. Although oligomers of the same molecular weight bury the same amounts of surface, the proportions buried within and between subunits vary. This has important implications for the role of subunit interfaces in the stability and activity of oligomeric proteins.
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