Fig. 5

Structure-based identification and classification of the abundant RBL protein family. a) Cladogram of Nosematida RBLs named based on available experimental data (PTP4, PTP5, PTP6, RBLL-1) and otherwise termed RBL1 through RBL9. Branches marked with stars indicate a bootstrap value > 70. Protein IDs with asterisks indicate existing publications on the respective gene, hashtag marks indicate previously identified orthologs to NbPTP6 [86], and proteins in bold with a light grey background indicate the corresponding ten most highly expressed genes during germination. b) Structure-based network of RBL domain folds color-coded according to their clade in a). Each node represents one RBL domain, connecting lines indicate the degree of structural relatedness, and surrounding shapes in brighter shades mark structural clusters. Protein folds of all RBLs identified in a) were predicted with AlphaFold and RBL domains were clustered according to structural similarity based on their TM score using Gephi (v0.9.2) [91]. RBL8 was excluded as the AlphaFold prediction was of very low confidence. c) AlphaFold-predicted protein structures for the PTP4s and PTP5s comparing tertiary structures of the RBL domain between the two protein families and the microsporidian families. E.c., Encephalitozoon cuniculi; E.h., Encephalitozoon hellem; E.r. Encephalitozoon romaleae; N.b., Nosema bombycis; O.c., Ordospora colligata; V.n., Vairimorpha necatrix; V.c., Vairimorpha ceranae; RBL, ricin B lectin; RBLL, ricin B lectin-like; PTP, polar tube protein