Capturing the Hierarchically Assorted Protein-protein Interaction Modules of Mammalian Cell

Proteins are organized into modules by both functions and physical interactions within compartments of an eukaryotic cell. The in vivo chemical crosslinking mass spectrometry (XL-MS) data collected from organelles, the whole cells and tissues are able to provide unique information about both protein-protein interaction (PPI) and the intensity of PPI. In the present study, we have retrieved 55,982 crosslinked peptides (XL-peptides) from the XL-MS databases, out of which 6,356 in vivo PPIs were identified. Introduction of the MONET software into analysis of 4,526 hetero PPIs revealed a total of 402 protein modules, including 15, 58 and 163 stable protein complex(s), condensate-forming protein module(s) and intrinsically disordered region (IDR)-containing protein module(s), respectively. The application of ChatGPT in analysis of these modules unexpectedly identified 4 vesicle-related modules. Together, these modules were assorted into 6 communities (module of modules) and 3 systems (module of communities) hierarchically. The bioinformatic analysis found that the three systems are corresponding to three compartments of eukaryotic cell: nuclei, mitochondria, endoplasmic reticulum (ER), respectively. This study presents a novel and comprehensive biomolecular modulome of a mammalian cell, which captures putative protein compositions of protein complexes, protein condensates and vesicles and provides a hierarchical protein organization and function within compartments of mammalian cell.