| Abstract |
Tim12 is a member of the family of small Tim proteins and resides in the mitochondrial intermembrane space. Tim12 is essential for life and plays a major part in the biogenesis of the organelle. It is peripherally bound to the mitochondrial inner membrane, as a constituent of the polytopic membrane protein insertion complex, TIM22. There is evidence for its role as a link between the soluble chaperone complex Tim9/Tim10 and Tim22 channel - that inserts the pre-proteins in the inner membrane. The exact role, though, of Tim12 during the stages of transport and membrane insertion of pre-proteins is still largely unknown. For the characterization of Saccharomyces cerevisiae Tim12, deletion mutants were studied, carrying deletions at amino- and carboxy termini, in order to identify regions important for the biogenesis and function of the protein. The four deletion mutants that were studied do not seem to affect import and proper sub-mitochondrial localization of Tim12. Deletion of C terminal 39 amino acids of Tim12 is lethal, as it fails to complement the deletion phenotype of the endogenous protein, while mutants with more extreme terminal deletions do not affect the growth of cells lacking chromosomally expressed Tim12. Furthermore, in vitro experiments showed that this mutant appears to affect the interaction between Tim12 and Tim9. In contrast with the deletions at extreme N- and C- termini, deletions involving more internal regions of the protein molecule abolish the ability of Tim12 to interact with liposomal membranes. The physiological relevance of the ability of Tim12 to interact with inner mitochondrial lipid bilayer is not clear. It seems that regions close to both N- and C- termini of Tim12 are necessary and in particular, the one close to C-terminal part is important for protein function.
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Λειτουργικός χαραρακτηρισμός της πρωτεϊνης Tim12 του Sacharomyces cerevisiae
