Functional nuclear suppressor of mitochondrial oxi2 mutations in yeast.

A semidominant nuclear suppressor, called nam6, of oxi2-V276 mitochondrial mutation has been isolated and characterized. The nuclear character of nam6 was proved by its retention in rho degree strains, lack of mitotic segregation in diploids and meiotic 2:2 segregation in tetrads. The specificity of nam6 was tested on 315 mit- mutations of four mitochondrial genes (oxi1, oxi2, oxi3, and cob-box). It suppresses clearly only three mutations in the oxi2 gene, restoring partially or completely cytochrome aa3 formation. The results suggest a functional character of the suppression.