scholarly journals Correlation of mitochondrial TOM core complex stop-and-go and open-closed channel dynamics

2021 ◽  
Author(s):  
Shuo Wang ◽  
Lukas Findeisen ◽  
Sebastian Leptihn ◽  
Mark I Wallace ◽  
Marcel Hörning ◽  
...  
Keyword(s):  
Protein Import ◽  
Mitochondrial Protein ◽  
Lateral Diffusion ◽  
Protein Diffusion ◽  
Channel Dynamics ◽  
Stop And Go ◽  
General Protein ◽  
Opening And Closing ◽  
The Relationship

The role of lateral diffusion of proteins in the membrane in the context of function has not been examined extensively. Here, we explore the relationship between protein lateral diffusion and channel activity of the general protein import pore of mitochondria (TOM-CC). Optical ion flux sensing through single TOM-CC molecules shows that TOM-CC can occupy three ion permeability states. Whereas freely diffusing TOM-CC molecules are preferentially found in a high permeability state, physical tethering to an agarose support causes the channels to transition to intermediate and low permeability states. This data shows that combinatorial opening and closing of the two pores of TOM-CC correlates with lateral protein diffusion in the membrane plane, and that the complex has mechanosensitive-like properties. This is the first demonstration of β-barrel protein mechanosensitivity, and has direct conceptual consequences for the understanding of the process of mitochondrial protein import. Our approach provides a novel tool to simultaneously study the interplay of membrane protein diffusion and channel dynamics.

scholarly journals Spatiotemporal Stop-and-go Dynamics of the Mitochondrial TOM Core Complex Correlates With Three-state Channel Activity

2021 ◽  
Author(s):  
Shuo Wang ◽  
Lukas Findeisen ◽  
Sebastian Leptihn ◽  
Mark Wallace ◽  
Marcel Hörning ◽  
...  
Keyword(s):  
Single Molecule ◽  
Protein Import ◽  
Protein Diffusion ◽  
Channel Activity ◽  
State Dependent ◽  
Stop And Go ◽  
Single Molecule Studies ◽  
General Protein ◽  
Opening And Closing ◽  
Permeability State

Abstract Single-molecule studies can reveal phenomena that remain hidden in ensemble measurements. Here, we show the correlation between lateral protein diffusion and channel activity of the general protein import pore of mitochondria (TOM-CC) in membranes resting on ultrathin hydrogel films. Using electrode-free optical recordings of ion flux, we find that TOM-CC switches reversibly between three states of ion permeability associated with protein diffusion. Freely diffusing TOM-CC molecules are observed in a high permeability state, while non-moving molecules are in an intermediate and a low permeability state. We explain this behavior by the mechanical binding of the two protruding Tom22 subunits to the hydrogel and a concomitant combinatorial opening and closing of the two β-barrel pores of TOM-CC. TOM-CC could thus be the first β-barrel protein channel to exhibit membrane state-dependent mechanosensitive properties.

scholarly journals Tim23–Tim50 pair coordinates functions of translocators and motor proteins in mitochondrial protein import

2009 ◽  
Vol 184 (1) ◽  
pp. 129-141 ◽  
Author(s):  
Yasushi Tamura ◽  
Yoshihiro Harada ◽  
Takuya Shiota ◽  
Koji Yamano ◽  
Kazuaki Watanabe ◽  
...  
Keyword(s):  
Motor Proteins ◽  
Protein Import ◽  
Protein Translocation ◽  
Mitochondrial Protein ◽  
Intermembrane Space ◽  
Mitochondrial Protein Import ◽  
Inner Membrane ◽  
The Matrix ◽  
General Protein ◽  
Mitochondrial Hsp70

Mitochondrial protein traffic requires coordinated operation of protein translocator complexes in the mitochondrial membrane. The TIM23 complex translocates and inserts proteins into the mitochondrial inner membrane. Here we analyze the intermembrane space (IMS) domains of Tim23 and Tim50, which are essential subunits of the TIM23 complex, in these functions. We find that interactions of Tim23 and Tim50 in the IMS facilitate transfer of precursor proteins from the TOM40 complex, a general protein translocator in the outer membrane, to the TIM23 complex. Tim23–Tim50 interactions also facilitate a late step of protein translocation across the inner membrane by promoting motor functions of mitochondrial Hsp70 in the matrix. Therefore, the Tim23–Tim50 pair coordinates the actions of the TOM40 and TIM23 complexes together with motor proteins for mitochondrial protein import.

scholarly journals ROMO1 is a constituent of the human presequence translocase required for YME1L protease import

2018 ◽  
Vol 218 (2) ◽  
pp. 598-614 ◽  
Author(s):  
Frank Richter ◽  
Sven Dennerlein ◽  
Miroslav Nikolov ◽  
Daniel C. Jans ◽  
Nataliia Naumenko ◽  
...  
Keyword(s):  
Membrane Structure ◽  
Protein Import ◽  
Protein Quality ◽  
Functional Characterization ◽  
Mitochondrial Protein ◽  
Mitochondrial Protein Import ◽  
Yeast Saccharomyces Cerevisiae ◽  
Inner Membrane ◽  
Inner Membrane Protein ◽  
General Protein

The mitochondrial presequence translocation machinery (TIM23 complex) is conserved between the yeast Saccharomyces cerevisiae and humans; however, functional characterization has been mainly performed in yeast. Here, we define the constituents of the human TIM23 complex using mass spectrometry and identified ROMO1 as a new translocase constituent with an exceptionally short half-life. Analyses of a ROMO1 knockout cell line revealed aberrant inner membrane structure and altered processing of the GTPase OPA1. We show that in the absence of ROMO1, mitochondria lose the inner membrane YME1L protease, which participates in OPA1 processing and ROMO1 turnover. While ROMO1 is dispensable for general protein import along the presequence pathway, we show that it participates in the dynamics of TIM21 during respiratory chain biogenesis and is specifically required for import of YME1L. This selective import defect can be linked to charge distribution in the unusually long targeting sequence of YME1L. Our analyses establish an unexpected link between mitochondrial protein import and inner membrane protein quality control.

scholarly journals Increased levels of the mitochondrial import factor Mia40 prevent the aggregation of polyQ proteins in the cytosol

2021 ◽  
Author(s):  
Anna M. Schlagowski ◽  
Katharina Knöringer ◽  
Sandrine Morlot ◽  
Ana Sáchez Vicente ◽  
Felix Boos ◽  
...  
Keyword(s):  
Protein Import ◽  
Mitochondrial Protein ◽  
Model System ◽  
Model Systems ◽  
Aggregate Formation ◽  
Mitochondrial Protein Import ◽  
Precursor Proteins ◽  
Polyq Protein ◽  
Rate Limiting

AbstractThe formation of protein aggregates is a hallmark of neurodegenerative diseases. Observations on patient material and model systems demonstrated links between aggregate formation and declining mitochondrial functionality, but the causalities remained unclear. We used yeast as model system to analyze the relevance of mitochondrial processes for the behavior of an aggregation-prone polyQ protein derived from human huntingtin. Induction of Q97-GFP rapidly leads to insoluble cytosolic aggregates and cell death. Although this aggregation impairs mitochondrial respiration only slightly, it interferes with efficient import of mitochondrial precursor proteins. Mutants in the import component Mia40 are hypersensitive to Q97-GFP. Even more surprisingly, Mia40 overexpression strongly suppresses the formation of toxic Q97-GFP aggregates both in yeast and in human cells. Based on these observations, we propose that the posttranslational import into mitochondria competes with aggregation-prone cytosolic proteins for chaperones and proteasome capacity. Owing to its rate-limiting role for mitochondrial protein import, Mia40 acts as a regulatory component in this competition. This role of Mia40 as dynamic regulator in mitochondrial biogenesis can apparently be exploited to stabilize cytosolic proteostasis. (174/175 words)

The Role of Molecular Chaperones in Mitochondrial Protein Import and Folding

1997 ◽  
pp. 127-193 ◽  
Author(s):  
Michael T. Ryan ◽  
Dean J. Naylor ◽  
Peter B. Høj ◽  
Margaret S. Clark ◽  
Nicholas J. Hoogenraad
Keyword(s):  
Molecular Chaperones ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Mitochondrial Protein Import
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