A protein isolated from a thermophilic bacterium shows a molecular weight of 160 kD when eluted from a size-exclusion chromatography column, but when the purified protein is run on an SDS-PAGE gel, a single band of 80 kD is observed. These results tell us that the protein is eluting from the size-exclusion column as a(monomer trimer dimer). The SDS-PAGE results allow us to conclude that the protein consists of identical (trimers monomers dimers), held together by (hydrophobic hydrophilic hydrogen bonding) interactions which are disrupted by the detergent during the SDS-PAGE procedure.