Isolation and Characterization of Mitochondrial Nucleoids from the Yeast Pichia jadinii

Mitochondrial (mt) nucleoids were isolated with a high degreeof purity from the yeast Pichia jadinii, in which the mitochondrialDNA (mtDNA) is linear. Field-inversion gel electrophoresis (FIGE)revealed that significant amounts of mtDNA could be isolatedintact, as linear molecules of 41 kbp, from the isolated mt-nucleoids.Fifteen different proteins were detected in the mt-nucleoidfraction and, eight of these proteins bound to DNA. The patternsof mt-nucleoid proteins and of the DNA-binding proteins aftergel electrophoresis in the presence of SDS were somewhat differentfrom those of such proteins from Saccharomyces cerevisiae. Thecorresponding proteins isolated from the mt-nucleoids of fourother species of yeast in the genera Pichia and Williopsis alsodiffered from one another in terms of electrophoretic mobilityin the presence of SDS. In immunoblotting experiments, antibodiesthat had been raised against the 67-kDa protein of mt-nucleoidsfrom S. cerevisiae and the YMN-1 monoclonal antibody that isspecific for a 48-kDa protein in the mt-nucleoids from S. cerevisiaedid not recognize any proteins in the mt-nucleoids from Pichiajadinii and four other species of yeast. The results suggestthe considerable diversity of the proteins in the mt-nucleoidsof yeasts. (Received March 28, 1996; Accepted June 19, 1996)