Abstract Nascent polypeptide associated complex (NAC) consisting of α- and β-subunits is an essential conserved ubiquitously expressed ribosome-associated protein in eukaryotes. NAC is considered as a chaperone and co-translational regulator of nascent protein sorting providing homeostasis of cellular proteins. Here we discovered the germinal cell specific NAC (gNAC) homologue, which differs from the ubiquitously expressed NAC by the presence of expanded intrinsically disordered regions (IDRs) at the N- and C-ends of the α- and β-subunits, respectively. We propose these evolutionary acquisition of long IDRs drive gNAC to endow both the specific conformational plasticity for binding client proteins and novel functions regulated by post-transcriptional modifications (PTM). At the same time, we demonstrated that the well-known lethal effect of the loss of ubiquitous NAC-β is suppressed by ectopic expression of its germinal paralog indicating the absence of strict functional differences between the ubiquitous and germline NAC-β subunit paralogs for protein homeostasis.

Detection of the germline specific NAC protein paralog enriched by intrinsically disordered regions inDrosophila melanogaster