The infuence of yeast rhomboid protease on the import of Tic40 into the yeast mitochondrion

Yeast rhomboid protease (Rbd1p) was found to act in the processing of Tic40 components in the yeast mitochondrion. Rhomboid protease was shown to have effects on the number of different Tic40 configurations displayed, the ratio of different configurations to one another and the targeting of Tic40 configurations within the yeast mitochondrion. The effects of Rbd1p on the ratio and targeting of different Tic40 configurations were also found to be dependent on the developmental stage of the yeast. Tic40 deletion constructs were expressed in yeast strains with active yeast rhomboid protease and in corresponding strains lacking Rbd1p. The processing of Tic40 differed between deletion constructs and between strains with and without yeast rhomboid protease. This indicates that rhomboid protease can affect the processing of Tic40 and the sequence of Tic40 can affect the activity of rhomboid protease with respect to Tic40. Tic40 is suspected to be involved in the regulation of plastid protein import. Rhomboid protease is shown here to affect the properties of Tic40 which have made it a candidate for a regulator of plastid protein import.