Identification of a Common Interactome of Beta-Actin and Its Prokaryotic Homolog MreB Reveals Conserved Physiological Functions of Actin Family of Cytoskeletal Proteins.

Bacterial actin-like proteins such as MreB and FtsA have been identified through structural homology to monomeric actin and their ability to form actin-like filaments. Furthermore, recent advances in structural biology have unearthed proteins that regulate the dynamics of these bacterial actin homologs much like their eukaryotic counterparts. However, questions remain as to how the actin and actin-like proteins evolved to participate in similar functions of cell division and maintenance of cell shape. To this effect, we asked whether the bacterial and eukaryotic actin homologs share a common interactome. Using previously published literature on functional homology followed by structural alignment of functional homologs, we identified 64 unique genetic and physical interactors of actin and their corresponding 38 homologs in bacteria that also interact with MreB/FtsA. We also report for the first time the identification of 10 bacterial homologs of 14 known actin interactors. Additionally, we reasoned that the homologous interactors would be essential to the function of actin. Therefore, the homologous interactors may show a high degree of co-expression with actin during cell division and differentiation, processes essential to embryogenesis. Therefore, we analysed the single-cell RNA expression data of early stages of human embryogenesis. We observed that ~66% of the homologous actin interactors showed positive correlation with the expression of beta-actin during early human embryogenesis. Taken together, our study not just enlists a common actin/MreB interactome, but also highlights the physiological significance of these interactions.