SUBUNIT STRUCTURE OF HALOPHILIC MALATE-DEHYDROGENASE FROM HALOARCULA-MARISMORTUI

1. The subunit structure of halophilic malate dehydrogenase from Haloarcula marismortui was studied by the method of crosslinking with bifunctional reagent. 2. Exposure of the enzyme to glutardialdehyde followed by sodium dodecyl sulphate gel electrophoresis resulted in the appearance of four bands with mobilities corresponding to monomeric polypeptide chains and crosslinked polypeptide chain dimers, trimers and tetramers. 3. Our findings are not consistent with the currently accepted dimeric structure of the enzyme. They provide a strong indication that halophilic malate dehydrogenase is composed of four identical subunits.