FUNCTIONAL COMPLEMENTATION OF A MEMBRANE-TRANSPORT DEFICIENCY IN SACCHAROMYCES-CEREVISIAE BY RECOMBINANT ND4 FUSION PROTEIN

ND4 is a mitochondrially encoded component of NADH dehydrogenase (Comp lex I) of the respiratory chain. A cDNA encoding a fusion protein comp rised of the N-terminus of GAL10 of Saccharomyces cerevisiae and an N- terminally truncated form of human ND4 was isolated by its ability to functionally complement the thymidine transport deficiency of S. cerev isiae grown under conditions of thymidylate starvation. Epitope-tagged GAL10-ND4 was shown by immunological methods to be present in the pla sma membranes of yeast expressing the GAL10-ND4 encoding cDNA. The abi lity of the GAL10-ND4 fusion protein to induce uptake of thymidine rai ses the possibility that native ND4, which is predicted to have 12 tra nsmembrane domains, may function as a transporter or channel in the mi tochondrial inner membrane. (C) 1997 Academic Press.