Mitochondrial presequences can induce aggregation of unfolded proteins

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Mitochondrial precursor proteins require targeting signals for import into mitochondria.
• These precursor proteins are synthesized in the cytosol in an unfolded state.
• The stability and folding of these precursor proteins in the cytosol are not fully understood.

Purpose of the Study:

• To investigate the interactions between synthetic peptides and unfolded proteins.
• To determine if mitochondrial presequences can induce protein aggregation.
• To elucidate the factors influencing presequence-mediated aggregation.

Main Methods:

• Studied interactions between synthetic peptides and model unfolded proteins (reduced and reduced/carboxymethylated alpha-lactalbumin).
• Assessed the effect of mitochondrial presequences on protein aggregation.
• Analyzed the role of electrostatic interactions and amphiphilicity in aggregation.

Main Results:

• Mitochondrial presequences induced aggregation of unfolded alpha-lactalbumin, but not native alpha-lactalbumin.
• Aggregation was dependent on electrostatic interactions and the amphiphilicity of the presequences.
• Positive charge and amphiphilicity are crucial for both presequence targeting and aggregation.

Conclusions:

• Mitochondrial presequences can cause aggregation of unfolded precursor proteins.
• This presequence-induced aggregation may contribute to the instability of mitochondrial precursor proteins in the cytosol.
• Inhibitory binding factors in the cytosol might be necessary to prevent such aggregation.