Mutational changes that affect the binding of the C2
fragment of
Streptococcal protein G (GB1) to the Fc domain of human IgG (IgG-Fc)
have been extensively studied using deep mutational scanning (DMS),
and the binding affinity of all single mutations has been measured
experimentally in the literature. To investigate the underlying molecular
basis, we perform in silico mutational scanning for all possible single
mutations, along with 2 μs-long molecular dynamics (WT-MD) of
the wild-type (WT) GB1 in both unbound and IgG-Fc bound forms. We
compute the hydrogen bonds between GB1 and IgG-Fc in WT-MD to identify
the dominant hydrogen bonds for binding, which we then assess in conformations
produced by Mutation and Minimization (MuMi) to explain the fitness
landscape of GB1 and IgG-Fc binding. Furthermore, we analyze MuMi
and WT-MD to investigate the dynamics of binding, focusing on the
relative solvent accessibility of residues and the probability of
residues being located at the binding interface. With these analyses,
we explain the interactions between GB1 and IgG-Fc and display the
structural features of binding. In sum, our findings highlight the
potential of MuMi as a reliable and computationally efficient tool
for predicting protein fitness landscapes, offering significant advantages
over traditional methods. The methodologies and results presented
in this study pave the way for improved predictive accuracy in protein
stability and interaction studies, which are crucial for advancements
in drug design and synthetic biology.