Protein–protein interactions
(PPIs) are involved
in almost
all biological processes in the cell. Understanding protein–protein
interactions holds the key for the understanding of biological functions,
diseases and the development of therapeutics. Recently, artificial
intelligence (AI) models have demonstrated great power in PPIs. However,
a key issue for all AI-based PPI models is efficient molecular representations
and featurization. Here, we propose Hom-complex-based
PPI representation, and Hom-complex-based machine
learning models for the prediction of PPI binding affinity changes
upon mutation, for the first time. In our model, various Hom complexes Hom(G
1, G) can be generated for the graph representation G of protein–protein complex by using different graphs G
1, which reveal G
1-related inner connections within the graph representation G of protein–protein complex. Further, for a specific
graph G
1, a series of nested Hom complexes are generated to give a multiscale characterization of
the PPIs. Its persistent homology and persistent Euler characteristic
are used as molecular descriptors and further combined with the machine
learning model, in particular, gradient boosting tree (GBT). We systematically
test our model on the two most-commonly used data sets, that is, SKEMPI
and AB-Bind. It has been found that our model outperforms all the
existing models as far as we know, which demonstrates the great potential
of our model for the analysis of PPIs. Our model can be used for the
analysis and design of efficient antibodies for SARS-CoV-2.