Tim17p regulates the twin pore structure and voltage gating of the mitochondrial protein import complex TIM23.
The TIM23 complex mediates import of preproteins into mitochondria, but little is known of the mechanistic properties of this translocase. Here patch clamping reconstituted inner membranes allowed for first time insights into the structure and function of the preprotein translocase. Our findings indicate that the TIM23 channel has "twin pores" (two equal sized pores that cooperatively gate) thereby strikingly resembling TOM, the translocase of the outer membrane. Tim17p and Tim23p are homologues, but their functions differ. Tim23p acts as receptor for preproteins and may largely constitute the preprotein-conducting passageway. Conversely depletion of Tim17p induces a collapse of the twin pores into a single pore, whereas N terminus deletion or C terminus truncation results in variable sized pores that cooperatively gate. Further analysis of Tim17p mutants indicates that the N terminus is vital for both voltage sensing and protein sorting. These results suggest that although Tim23p is the main structural unit of the pore Tim17p is required for twin pore structure and provides the voltage gate for the TIM23 channel.
Martinez-Caballero
Sonia
S
Department of Basic Sciences, New York University College of Dentistry, New York, New York 10010, USA.
Grigoriev
Sergey M
SM
Herrmann
Johannes M
JM
Campo
María Luisa
ML
Kinnally
Kathleen W
KW
D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D018408:Patch-Clamp Techniques; D011498:Protein Precursors / Q000378:metabolism / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology
D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D011498:Protein Precursors; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; C091191:TIM17 protein, S cerevisiae; C083081:TIM23 protein, S cerevisiae