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Cytolysin/lectin superfamily

SCOP classification
Root:   SCOP hierarchy in SUPERFAMILY [ 0] (11)
Class:   All beta proteins [ 48724] (174)
Fold:   Cytolysin/lectin [ 63723]
Superfamily:   Cytolysin/lectin [ 63724] (2)
Families:   Anemone pore-forming cytolysin [ 63725] (2)
  Fungal fruit body lectin [ 117119] (2)

Superfamily statistics
Genomes (64) Uniprot 2018_03 genome PDB chains (SCOP 1.75)
Domains 122 529 6
Proteins 122 524 6

Functional annotation
General category Processes_EC
Detailed category Toxins/defense

Function annotation of SCOP domain superfamilies

InterPro annotation
Cross references IPR009104 SSF63724 Protein matches

Sea anemones are a rich source of lethal pore-forming peptides and proteins, known collectively as cytolysins or actinoporins. There are several different groups of cytolysins based on their structure and function [PubMed11689232]. This entry represents the most numerous group, the 20-kDa highly basic peptides. These cytolysins form cation-selective pores in sphingomyelin-containing membranes. Examples include equinatoxins (from Actinia equina), sticholysins (from Stichodactyla helianthus), magnificalysins (from Heteractis magnifica), and tenebrosins (from Actinia tenebrosa), which exhibit pore-forming, haemolytic, cytotoxic, and heart stimulatory activities.

Cytolysins adopt a stable soluble structure, which undergoes a conformational change when brought in contact with a membrane, leading to an active, membrane-bound form that inserts spontaneously into the membrane. They often oligomerise on the membrane surface, before puncturing the lipid bilayers, causing the cell to lyse. The 20-kDa sea anemone cytolysins require a phosphocholine lipid headgroup for binding, however sphingomyelin is required for the toxin to promote membrane permeability [PubMed14604518]. The crystal structures of equinotoxin II [PubMed11827489] and sticholysin II [PubMed14604522] both revealed a compact beta-sandwich consisting of ten strands in two sheets flanked on each side by two short alpha-helices, which is a similar topology to osmotin. It is believed that the beta sandwich structure attaches to the membrane, while a three-turn alpha helix lying on the surface of the beta sheet may be involved in membrane pore formation, possibly by the penetration of the membrane by the helix.

InterPro database

PDBeMotif information about ligands, sequence and structure motifs
Cross references PDB entries
Ligand binding statistics
Nucleic-acid binding statistics
Occurrence of secondary structure elements
Occurrence of small 3D structural motifs

PDBeMotif resource

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Internal database links

Browse genome assignments for this superfamily. The SUPERFAMILY hidden Markov model library has been used to carry out SCOP domain assignments to all genomes at the superfamily level.

Alignments of sequences to 7 models in this superfamily are available by clicking on the 'Alignments' icon above. PDB sequences less than 40% identical are shown by default, but any other sequence(s) may be aligned. Select PDB sequences, genome sequences, or paste in or upload your own sequences.

Browse and view proteins in genomes which have different domain combinations including a Cytolysin/lectin domain.

Examine the distribution of domain superfamilies, or families, across the major taxonomic kingdoms or genomes within a kingdom. This gives an immediate impression of how superfamilies, or families, are restricted to certain kingdoms of life.

Explore domain occurrence network where nodes represent genomes and edges are domain architectures (shared between genomes) containing the superfamily of interest.

There are 7 hidden Markov models representing the Cytolysin/lectin superfamily. Information on how the models are built, and plots showing hydrophobicity, match emmission probabilities and insertion/deletion probabilities can be inspected.

Jump to [ Top of page · SCOP classification · InterPro annotation · PDBeMotif links · Functional annotation · Internal database links ]