Identification, Expression, and Import of Components 17 and 23 of the Inner Mitochondrial Membrane Translocase from Arabidopsis

• Published in: Plant physiology (Bethesda) Vol. 131; no. 4; pp. 1737 - 1747
• Main Authors: Monika W. Murcha, Ryan Lister, Angela Y. Y. Ho, Whelan, James
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.04.2003; American Society of Plant Physiologists
• Subjects: Amino acids; Arabidopsis - cytology; Arabidopsis - genetics; Arabidopsis - metabolism; Biological and medical sciences; Biological Transport, Active; Cell biochemistry; Cell Biology and Signal Transduction; Cell physiology; Complementation; Fundamental and applied biological sciences. Psychology; Gene Expression; Genetic Complementation Test; Genomes; Glycine max - genetics; Glycine max - metabolism; Imports; Intracellular Membranes - metabolism; Mitochondria; Mitochondria - metabolism; Mitochondrial Membrane Transport Proteins - genetics; Mitochondrial Membrane Transport Proteins - metabolism; Plant physiology and development; Polymerase chain reaction; Proteins; rev genes; Sequence Homology; Soybeans; Yeasts; Yeasts - genetics; Yeasts - metabolism; Membrane protein; Identification; Structure function relationship; Internal membrane; Fungi; Arabidopsis thaliana; Characterization; Mitochondria; Cruciferae; Dicotyledones; Angiospermae; Ascomycetes; Developmental stage; Molecular cloning; Carrier protein; Aminoacid sequence; Thallophyta; Translocation; Leader peptide; Intracellular transport; Interspecific comparison; Tissue specificity; Gene expression; Spermatophyta; Experimental plant; Molecular domain; Saccharomyces cerevisiae
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.102.016808

Characterization of components 17 and 23 of the inner mitochondrial membrane translocase (TIM17:23) from Arabidopsis indicated that there were three genes present for TIM17 and TIM23 and two for TIM44. AtTIM17 differed from the yeast (Saccharomyces cerevisiae) and mammalian homologs in that two genes encoded proteins that were longer and one gene encoded a shorter protein. All Arabidopsis TIM23 predicted proteins appeared to lack the first 34 amino acids compared with yeast TIM23. All AtTIM17 and AtTIM23 genes were expressed but displayed different tissue and developmental profiles. Complementation of deletion mutants in yeast indicated that for AtTIM17, the extension at the C terminus not present in yeast had to be removed to achieve complementation, whereas for TIM23, a preprotein and amino acid transporter domain had to be present for complementation. Import assays with AtTIM17 and AtTIM23 indicated that they both contained internal signals for integration into the inner mitochondrial membrane in a membrane potential-dependent manner. The C terminus of imported AtTIM17-2 was susceptible to degradation by externally added protease with intact mitochondria. Removal of the 85 C-terminal amino acids resulted in import and full protection of the truncated protein. This suggests that the novel extension at the C terminus of AtTIM17-2 links the outer and inner membrane in a manner analogous to yeast TIM23.