Thaumatin family
SMART accession number:SM00205
Description: The thaumatin family gathers proteins related to plant pathogenesis. The thaumatin family includes very basic members with extracellular and vacuolar localization. Thaumatin itsel is a potent sweet-tasting protein. Several members of this family display significant in vitro activity of inhibiting hyphal growth or spore germination of various fungi probably by a membrane permeabilizing mechanism.
Interpro abstract (IPR001938):

Thaumatin [ (PUBMED:7049841) ] is an intensely sweet-tasting protein, 100 000 times sweeter than sucrose on a molar basis [ (PUBMED:7049841) ], found in berries from Thaumatococcus daniellii, a tropical flowering plant known as Katemfe. It is induced by attack by viroids, which are single-stranded unencapsulated RNA molecules that do not code for protein.

Thaumatin consists of about 200 residues and contains 8 disulphide bonds. Like other PR proteins, thaumatin is predicted to have a mainly beta structure, with a high content of beta-turns and little helix [ (PUBMED:7049841) ]. Several stress-induced proteins of plants have been found to be related to thaumatins:

  • A maize alpha-amylase/trypsin inhibitor
  • Two tobacco pathogenesis-related proteins: PR-R major and minor forms,which are induced after infection with viruses
  • Salt-induced protein NP24 from tomato
  • Osmotin, a salt-induced protein from tobacco[ (PUBMED:16666857) ]
  • Osmotin-like proteins OSML13, OSML15 and OSML81 from potato [ (PUBMED:7630973) ]
  • P21, a leaf protein from soybean
  • PWIR2, a leaf protein from wheat [ (PUBMED:1650615) ]
  • Zeamatin, a maize antifunal protein [ (PUBMED:7846159) ]

This family is also referred to as pathogenesis-related group 5 (PR5), as many thaumatin-like proteins accumulate in plants in response to infection by a pathogen and possess antifungal activity [ (PUBMED:1463856) ]. The proteins are involved in systematically acquired resistance and stress response in plants, although their precise role is unknown [ (PUBMED:1463856) ]. The PR5K receptor protein kinase from Arabidopsis comprises an extracellular domain related to the PR5 proteins, and an intracellular protein-serine/threonine kinase domain [ (PUBMED:8637920) ].

Family alignment:
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There are 4478 THN domains in 4421 proteins in SMART's nrdb database.

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