PMID:10409639

Citation	Lee, CM, Sedman, J, Neupert, W and Stuart, RA (1999) The DNA helicase, Hmi1p, is transported into mitochondria by a C-terminal cleavable targeting signal. J. Biol. Chem. 274:20937-42
Abstract	We have identified a novel mitochondrial targeting signal in the precursor of the DNA helicase Hmi1p of Saccharomyces cerevisiae that is located at the C terminus of the protein. Similar to classical N-terminal presequences, this C-terminal targeting signal consists of a stretch of positively charged amino acids that has the potential to form an amphipathic alpha-helix. Deletion of the C-terminal 36 amino acids of helicase resulted in loss of import into mitochondria, while deletion of the N-terminal 40 amino acids had no effect. When C-terminal regions of the helicase were placed at the C terminus of a passenger protein, dihydrofolate reductase, the resulting fusion proteins were directed into the mitochondrial matrix, and the C-terminal region of helicase became proteolytically processed. Import of helicase occurs in a C- to N-terminal direction; it requires a membrane potential and the TIM17-23 translocase together with mitochondrial Hsp70. Helicase is the only mitochondrial matrix protein identified thus far with a cleavable targeting signal at its C terminus.
Links	PubMed
Keywords	Amino Acid Sequence; Biological Transport; DNA Helicases/genetics; DNA Helicases/metabolism; Fungal Proteins/genetics; Fungal Proteins/metabolism; Mitochondria/metabolism; Mitochondrial Proteins; Molecular Sequence Data; Saccharomyces cerevisiae/metabolism; Saccharomyces cerevisiae/ultrastructure; Saccharomyces cerevisiae Proteins
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