Structure of a proteasome Pba1-Pba2 complex: implications for proteasome assembly, activation, and biological...

Area of Science:

• Biochemistry
• Cell Biology
• Molecular Biology

Background:

• The 20S proteasome is a crucial protease with sequestered active sites, requiring activators to open its gate for substrate degradation.
• Known activators like Blm10 and PAN/19S use C-terminal HbYX motifs to bind proteasome α-subunits and open the gate.
• Pba1 and Pba2 proteins, implicated in proteasome assembly, also possess HbYX motifs.

Purpose of the Study:

• To investigate the interaction between Pba1-Pba2 proteins and the 20S proteasome.
• To determine the role of Pba1-Pba2 HbYX motifs in proteasome function, particularly in mitochondrial maintenance.
• To elucidate the structural basis of Pba1-Pba2 binding to the 20S proteasome.

Main Methods:

• In vitro binding assays to assess Pba1-Pba2 heterodimer interaction with 20S proteasomes.
• Crystallography to determine the structure of the proteasome Pba1-Pba2 complex.
• Analysis of proteasome function in mitochondrial maintenance.

Main Results:

• Pba1-Pba2 forms a stable heterodimer that binds to mature 20S proteasomes via its HbYX motifs.
• The Pba1-Pba2 interaction is vital for the proteasome's role in maintaining mitochondrial function.
• Crystal structure reveals conserved Pba1 HbYX binding and a novel Pba2 HbYX interaction, with gate disruption but not full opening.

Conclusions:

• Pba1-Pba2 proteins interact with 20S proteasomes through HbYX motifs, influencing mitochondrial function.
• The findings suggest a broader role for Pba1-Pba2 beyond assembly, potentially involving mitochondrial regulation pathways.
• The study extends the understanding of HbYX motif interactions with proteasomes and highlights multifaceted roles of Pba1-Pba2.