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The N‐terminal region of the Trypanosoma brucei Tim17 is critical for mitochondrial protein import (950.3)
Author(s) -
Weems Ebony
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.950.3
Subject(s) - trypanosoma brucei , biology , saccharomyces cerevisiae , gene knockdown , mutant , inner mitochondrial membrane , microbiology and biotechnology , rna interference , mitochondrion , amino acid , mitochondrial carrier , biochemistry , gene , rna , bacterial outer membrane , escherichia coli
The protein translocases of the mitochondrial inner membrane in higher eukaryotes, TIM23‐17 and TIM22‐54, possess three homologous proteins, Tim17, Tim23, and Tim22. In contrast, Trypanosoma brucei , a parasitic protozoon that causes African trypanosomiasis, possesses a single homologue of this protein family, TbTim17. TbTim17 is a part of a large protein complex consisting of proteins unique to trypanosomes. In spite of a significant similarity in the secondary structure of TbTim17 with the Tim17/23/22 family proteins, we report here that the growth defect caused by TbTim17 knockdown in T. brucei could not be complemented by the expression of either Tim17, or Tim23, or Tim22 from Saccharomyces cerevisiae and vice versa, suggesting TbTim17 is significantly divergent in order to full‐fill the species‐specific functions. Bioinformatics analysis revealed that TbTim17 N‐terminus possesses a longer stretch of hydrophilic amino acids at this domain (~30 amino acids) relative to Tim17 proteins expressed in other eukaryotes. In order to investigate the function of this region we expressed a number of N‐terminal deletion mutants of TbTim17 in T. brucei , where endogenous TbTim17 was knockdown by RNA interference targeted to the 3’‐untranslated region of its transcript. We found that the growth defect caused by TbTim17 RNAi was completely rescued by ectopic expression of the full‐length TbTim17 (FL‐TbTim17) but not by the N‐terminal deletion mutants, 20TbTim17, and 30TbTim17. All of these mutants are expressed and properly targeted to mitochondrial membrane in T. brucei . However, the import of nucleus‐encoded mitochondrial proteins into the mitochondrion is significantly inhibited in the N‐terminal deletion mutants. Suggesting a critical role for this region in the import of mitochondrial proteins in T. brucei . Grant Funding Source : 2SC1GM081146, 5T32HL007737, 5T32AI007281, and 2R25GM059994