Exploring the Landscape of the PP7 Virus-like Particle for Peptide Display

Area of Science:

• Biotechnology
• Structural Biology
• Protein Engineering

Background:

• Self-assembling virus-like particles (VLPs) offer a versatile platform for displaying foreign molecules due to their adaptable capsid proteins.
• Previous work demonstrated successful peptide display on PP7 dimer VLPs at specific accessible regions.
• Understanding assembly tolerance to capsid modifications is crucial for VLP engineering.

Purpose of the Study:

• To investigate the assembly tolerance of PP7 dimer capsid proteins to randomized 15-mer peptide insertions and terminal extensions.
• To identify sequence preferences and constraints for successful VLP assembly with surface-displayed peptides.
• To expand the repertoire of peptides displayable on PP7 dimer VLPs.

Main Methods:

• Implementation of a library-based approach using randomized 15-mer peptide sequences.
• Two iterative rounds of assembly-based selection to identify functional VLP sequences.
• Deep sequencing analysis to evaluate amino acid preferences at each position within the displayed peptides.

Main Results:

• Identified a distinct preference for hydrophilic peptides and negatively charged amino acids (Asp, Glu) in assembly-competent VLPs.
• Observed exclusion of positively charged, bulky, and hydrophobic amino acid residues (Trp, Phe, Tyr, Cys).
• Discovered 4,000 to 22,000 unique 15-mer peptide sequences successfully displayed on PP7 dimer capsids.

Conclusions:

• PP7 dimer capsid proteins exhibit specific sequence preferences for accommodating surface-displayed peptides.
• Small initial libraries can yield a large number of assembly-competent VLP sequences.
• This library-based selection method significantly expands the known diversity of displayable peptides on nucleoprotein particles.