Hybridization in vitro between Wild-Type and Mutant Forms of Glutamate Dehydrogenase from Neurospora crassa

Markert (1963) has demonstrated that the five electrophoretically distinct forms of lactate de- hydrogenase from ox tissues (L-lactate-NAD oxidoreductase, EC 1.1.1.27)are made up of all the possible tetramers of two basic sub-units A and B. The two extreme forms A4 and B4 show a large difference in electrophoretic mobility on starch gels at pH 8-6.On freezing and thawing a 1:1 mixture of A4 and B4 in the presence of m-NaCl-0-1M-phosphate buffer, pH 7-0, there was a dissociation into sub-units and a random reassociation to give the five possible species, A4, A3B, A2B2, AB3 and B4 in the binomial propor- tions 1:4:6:4:1.The three hybrid species had electrophoretic mobilities intermediate between those of A4 and B4.This work was amplified by Chilson, Costello & Kaplan (1965), who defined more closely the conditions required for random hybridization.