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Yeast killer toxins superfamily

SCOP classification
Root:   SCOP hierarchy in SUPERFAMILY [ 0] (11)
Class:   Alpha and beta proteins (a+b) [ 53931] (376)
Fold:   Yeast killer toxins [ 55220]
Superfamily:   Yeast killer toxins [ 55221] (2)
Families:   Virally encoded KP4 toxin [ 55222]
  SMK toxin [ 55225]

Superfamily statistics
Genomes (38) Uniprot 2018_03 genome PDB chains (SCOP 1.75)
Domains 79 384 3
Proteins 68 333 3

Functional annotation
General category Processes_EC
Detailed category Toxins/defense

Function annotation of SCOP domain superfamilies

InterPro annotation
Cross references IPR011329 SSF55221 Protein matches

This entry represents a structural fold found in the killer toxins Kp4 and SMK, consisting of two left-handed split beta/alpha/beta motifs, which is rarely found in other toxins; hence, these toxins may be evolutionarily or functionally related [PubMed9016714]. Killer toxins are polypeptides secreted by some fungal species that kill sensitive cells of the same or related species, often functioning by creating pores in target cell membranes.

The fungal killer toxin KP4 from the corn smut fungus, Ustilago maydis (Smut fungus), is encoded by a resident symbiotic double-stranded RNA virus, Ustilago maydis P4 virus (UmV4), within fungal cells. Unlike most killer toxins, KP4 is a single polypeptide [PubMed8145639]. KP4 inhibits voltage-gated calcium channels in mammalian cells, which in turn inhibits cell growth and division by blocking calcium import. KP4 adopts a structure consisting of a two-layer alpha/beta sandwich with a left-handed crossover [PubMed7582897].

The killer toxin SMK (salt-mediated killer) from the halotolerant yeast Pichia farinosa acts to kill sensitive strains of yeast. SMK exhibits maximum activity under conditions of acidic pH and high salt concentration. It is composed of two distinct subunits, alpha and beta, which tightly interact with each other under acidic conditions, jointly folding into an ellipsoidal single domain structure belonging to the alpha/beta-sandwich family. SMK appears to function by associating with the membranes of sensitive cells [PubMed11748724].

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

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

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 2 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 Yeast killer toxins 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 2 hidden Markov models representing the Yeast killer toxins 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 ]