Malate Dehydrogenase: Evidence for Tetrameric Structure in Mus Musculus

Two electrophoretically distinct variants of supernatant nicotinamideadenine dinucleotide phosphate-dependent malate dehydrogenase exist in mice (Mus musculus). They are controlled by codominant alleles segregating at an autosomal locus. The two forms exist in a polymorphic condition in wild populations of Mus musculus and are fixed in a homozygous condition in inbred lines. These genetic electrophoretic variants are used here to study the subunit structure of this enzyme. Evidence indicating a tetrameric structure for mouse nicotinamideadenine dinucleotide phosphate-dependent malate dehydrogenase is presented. This interpretation is based on the occurrence in heterozygote tissue extracts of five electrophoretically distinct enzymes. This is the predicted phenotype for tetramers composed of two types of subunits which associate randomly in heterozygotes forming three hybrid enzymes having mobilities intermediate between the parental forms.