Identification and characterisation of a novel EhOrc1/Cdc6 from the human pathogen Entamoeba histolytica: an in...

The onset of a pre-replication complex on origin commences DNA replication. The Origin recognition complex (Orc), Cell division cycle protein 6 (Cdc6), and the minichromosome maintenance (Mcm) replicative helicase, along with Chromatin licensing and DNA replication factor 1 (Cdt1), make up the pre-replication complex in eukaryotes. Eukaryotic Orc is made up of six subunits, designated Orc1-6 while monomeric Cdc6 has sequence similarity with Orc1. However, Orc has remained unexplored in the protozoan parasite Entamoeba histolytica. Here we report a single functional Orc1/Cdc6 protein in E. histolytica. Its structural and functional aspects have been highlighted by a detailed in silico analysis that reflects physicochemical characteristics, predictive 3D structure modelling, protein-protein interaction studies, molecular docking and simulation. This in silico study provides insight into EhOrc1/Cdc6 and points out that E. histolytica carries pre-replication machinery that is less complex than higher eukaryotes and closer to archaea. Additionally, it lays the groundwork for future investigations into the methods of origin recognition, and anomalies of cell cycle observed in this enigmatic parasite.Communicated by Ramaswamy H. Sarma.