Fig. 1

Genomic evolution of subtilisin-like prohormone convertases. A Gene tree (based on protein sequence retrieved from Genbank nr database and ENSMBL proteins between 06-2020 and 12-2020) showing the clustering of prohormone convertases and furins in different animal groups, including most major insect taxa. SKI-1-proteins were used as outgroup. Node labels indicate local bootstrap support values. Full species names and protein sequences used in the alignment are given in Additional file 1: Table S1. B Table showing presence/absence distribution of PC-orthologues in insects and other animal groups (*classification of C. elegans proteins is based on [4]). Overall, the system is conserved. A PC1/3 but no PC2 orthologue is present in cnidarians, identifying PC1/3 as the evolutionarily older convertase. Only dipterans and C. elegans have lost PC1/3. All insects have lost the PC7 genes, whereas it was retained in the myriapod Strigamia maritima and the lophotrochozoan Lottia gigantea. A group of basal PCs closely related to PC7 genes is present in the Cnidarian Nematostella. The myriapod Strigamia maritima and the mayfly Cloeon dipterum have sequences that appear to be closely related to PC7 proteins and pre-bilaterian basal PCs. The bilaterian invertebrate species each have furin1 and furin2, whereas only 1 furin protein is present in the cnidarians. Vertebrate furins have diverged into furin and PC4 (related to invertebrate furin2) as well as PC5 and PACE4 (related to invertebrate furin1). **The Orchesella cincta sequence (uncl.PC_Orchesella, see tree in A does not group with any of the subgroups. Based on the presence of a second furin1 gene in the other included collembolan Folsomia candida (furin1-2_Folsomia) we assume that the Orchesella sequence might be a derived furin1 duplicate, even though this is not supported by the alignment). *** A second Chloeon PC1/3 sequence might be an assembly artefact (see suppl. material 1). All cartoons credited to PhyloPic/free licence, hemipteran: K. Garcia/PhyloPic. C Protein structure of Tribolium PC1/3 and PC2 in comparison to vertebrate (mouse) PC1/3 and PC2, showing the N-terminal Signal Peptide (SP), S8-pro domain, S8-peptidase domain, the P/homo B regulatory domain, and a prohormone domain (proho) present in mouse PC2. A specific sequence motif including -RRGDL- conserved in vertebrates and possibly involved in the sorting of the proteins to secretory vesicles [27] is present in Tribolium PC2 but not PC1/3