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Assessment of Submitochondrial Protein Localization in Budding Yeast Saccharomyces cerevisiae
Published on: July 19, 2021
Structural basis for the function of Tim50 in the mitochondrial presequence translocase
Xinguo Qian1, Michael Gebert, Jan Höpker
1Department of Cell Biology, University of Alabama at Birmingham, 1918 University Boulevard, Birmingham, AL 35294-0005, USA.
Journal of Molecular Biology
|June 28, 2011
Summary
Researchers determined the crystal structure of yeast Tim50, revealing a β-hairpin crucial for cooperation with Tim23. This interaction facilitates mitochondrial protein import through the inner membrane.
Area of Science:
- Mitochondrial biology
- Protein import
- Structural biology
Background:
- Mitochondrial proteins are synthesized in the cytosol with presequences.
- Import involves outer and inner membrane translocases.
- Tim50 and Tim23 mediate intermembrane space transfer.
Purpose of the Study:
- To elucidate the structural basis of Tim50 and Tim23 cooperation.
- To understand the mechanism of preprotein translocation.
Main Methods:
- X-ray crystallography
- Determination of yeast Tim50 intermembrane space domain structure at 1.83 Å resolution.
Main Results:
- The crystal structure of the yeast Tim50 intermembrane space domain was determined.
- A protruding β-hairpin in Tim50 was identified as critical for Tim23 interaction.
- This interaction provides a molecular explanation for cooperative preprotein translocation.
Conclusions:
- The β-hairpin of Tim50 is essential for its interaction with Tim23.
- This structural insight clarifies the mechanism of mitochondrial preprotein translocation.
- The findings contribute to understanding protein import into mitochondria.
Related Concept Videos
01:34Protein Transport into the Inner Mitochondrial Membrane
Nuclear encoded mitochondrial precursors are imported to the inner membrane in a multistep process involving two separate translocons, TIM22 and TIM23. TIM23 is a cation-selective pore that remains closed by the N terminal segment of the protein. Negative charges on the TIM23 act as a receptor for the incoming precursor, pulling the positively charged matrix-targeting sequence for peptide insertion and translocation.
Transport of mitochondrial precursors across the TIM23 channel is driven by...
Transport of mitochondrial precursors across the TIM23 channel is driven by...
01:19Translocation of Proteins into the Mitochondria
Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
01:39Mitochondrial Protein Sorting
Mitochondria are double-membrane organelles of the eukaryotes involved in cellular metabolism, signaling, ATP synthesis, and programmed cell death. Each of these processes requires specific proteins and enzymes that must be correctly sorted to the right mitochondrial subcompartment for the proper functioning of the organelle.
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
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01:37Energy to Drive Translocation
Mitochondrial protein import is powered by two distinct energy sources: ATP hydrolysis and electrochemical potential across the inner membrane. Newly synthesized precursors are bound by cytosolic chaperones of the Hsp70 family, which guide them to the import receptors on the mitochondrial surface. Utilizing the energy of ATP hydrolysis, Hsp70 chaperones transfer these precursors to the TOM receptors on the mitochondrial outer membrane.
Generally, polypeptides are unfolded by two distinct...
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01:39Mitochondrial Precursor Proteins
Mitochondrial precursors are partially unfolded or loosely folded polypeptide chains. Newly synthesized precursors are inhibited from spontaneously folding into their native conformation by the cytosolic chaperones, heat shock proteins 70 (Hsp70), and mitochondrial import stimulation factors (MSFs). Precursors bound to MSFs are guided to the TOM70-TOM37 receptors, while precursors bound to Hsp70 chaperones are targetted to TOM20-TOM22 receptor complexes.
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