Characterization of Signal That Directs C-Tail–anchored Proteins to Mammalian Mitochondrial Outer Membrane

AUTOR(ES)

Horie, Chika

FONTE

The American Society for Cell Biology

RESUMO

We analyzed the signal that directs the outer membrane protein with the C-terminal transmembrane segment (TMS) to mammalian mitochondria by using yeast Tom5 as a model and green fluorescent protein as a reporter. Deletions or mutations were systematically introduced into the TMS or the flanking regions and their intracellular localization in COS-7 cells was examined using confocal microscopy and cell fractionation. 1) Three basic amino acid residues within the C-terminal five-residue segment (C-segment) contained the information required for mitochondrial-targeting. Reduction of the net positive charge in this segment decreased mitochondrial specificity, and the mutants were distributed throughout the intracellular membranes. 2) Elongation of the TMS interfered with the function of the C-segment and the mutants were delivered to the intracellular membranes. 3) Separation of the TMS and C-segment by linker insertion severely impaired mitochondrial targeting function, leading to mislocalization to the cytoplasm. 4) Mutations or small deletions in the region of the TMS flanking the C-segment also impaired the mitochondrial targeting. Therefore, the moderate length of the TMS, the positive charges in the C-segment, and the distance between or context of the TMS and C-segment are critical for the targeting signal. The structural characteristics of the signal thus defined were also confirmed with mammalian C-tail–anchored protein OMP25.

Documentos Relacionados

• Targeting of a Tail-anchored Protein to Endoplasmic Reticulum and Mitochondrial Outer Membrane by Independent but Competing Pathways
• Two Endoplasmic Reticulum (ER) Membrane Proteins That Facilitate ER-to-Golgi Transport of Glycosylphosphatidylinositol-anchored Proteins
• Yeast mitochondrial outer membrane specifically binds cytoplasmically-synthesized precursors of mitochondrial proteins
• Tromp1, a putative rare outer membrane protein, is anchored by an uncleaved signal sequence to the Treponema pallidum cytoplasmic membrane.
• Metalloadsorption by Escherichia coli Cells Displaying Yeast and Mammalian Metallothioneins Anchored to the Outer Membrane Protein LamB