Elucidating the Key Determinants of Structure, Folding, and Stability for the ( $4\beta + \alpha $ ) Conformation of the B1 Domain of Protein G Using Bioinformatics Approaches

The B1 domain of protein G (GB1) is a small, 56 amino acid bacterial immunoglobulin-binding protein with a 4β + α fold. Architecturally, it is composed of a two-layer sandwich consisting of a four-stranded β-sheet that packs against an α-helix. Using several bioinformatics approaches, we investigated which residues may be key determinants of this fold. We identified nine structurally conserved amino acids using a conservation analysis and propose they are critical to forming and stabilizing the fold. The nine conserved residues form a predominantly hydrophobic nucleus within the core of GB1. A network analysis of all the long-range interactions in the structure of GB1 in concert with a betweenness centrality analysis revealed the relative significance of each conserved amino acid residue based on the number and location of the interactions. This bioinformatics analysis provides an important foundation for the design and interpretation of both computational and experimental work which may be helpful in solving the protein folding problem.