Yeast mitochondria can process de novo designed β-barrel proteins

Area of Science:

• Cell Biology
• Molecular Biology
• Protein Biogenesis

Background:

• Mitochondrial outer membrane beta-barrel proteins are synthesized in the cytosol and imported into mitochondria.
• Understanding the general biogenesis of beta-barrel proteins is crucial for comprehending organelle function.
• De novo designed beta-barrel proteins offer a tool to investigate fundamental protein targeting and insertion mechanisms.

Purpose of the Study:

• To investigate the cellular fate and mitochondrial targeting of de novo designed beta-barrel proteins in yeast.
• To determine the role of the yeast mitochondrial protein import machinery in the biogenesis of these artificial proteins.

Main Methods:

• Expression of de novo designed beta-barrel proteins (Tmb2.3 and Tmb2.17) in yeast cells.
• Analysis of protein localization to mitochondria using cell biology techniques.
• Investigating the requirement of mitochondrial import components (Tom20, Tom70, Tob55/Sam50, Mas37/Sam37) for protein biogenesis.

Main Results:

• De novo designed beta-barrel proteins were successfully targeted to and integrated into the yeast mitochondrial outer membrane.
• The import receptors Tom20 and Tom70 were not essential for the biogenesis of these artificial proteins.
• The TOB/SAM complex (Tob55/Sam50 and Mas37/Sam37) was found to be essential for the integration of these proteins.

Conclusions:

• The mitochondrial outer membrane serves as a preferred destination for any membrane-embedded beta-barrel protein in yeast.
• The TOB/SAM complex plays a critical role in the insertion of beta-barrel proteins into the mitochondrial outer membrane, regardless of their origin.
• These findings provide insights into the general principles governing beta-barrel protein biogenesis and mitochondrial targeting.