Biological Role
Thaumatin production is induced in katemfe in response to an attack upon the plant by viroid pathogens. Several members of the thaumatin protein family display significant in vitro inhibition of hyphal growth and sporulation by various fungi. The thaumatin protein is considered a prototype for a pathogen-response protein domain. This thaumatin domain has been found in species as diverse as rice and Caenorhabditis elegans. Thaumatins are pathogenesis-related (PR) proteins, which are induced by various agents ranging from ethylene to pathogens, and are structurally diverse and ubiquitous in plants: They include thaumatin, osmotin, tobacco major and minor PR proteins, alpha-amylase/trypsin inhibitor, and P21 and PWIR2 soybean and wheat leaf proteins. The proteins are involved in systematically acquired resistance and stress response in plants, although their precise role is unknown. Thaumatin is an intensely sweet-tasting protein (on a molar basis about 100,000 times as sweet as sucrose) found in the West African shrub Thaumatococcus daniellii: it is induced by attack by viroids, which are single-stranded unencapsulated RNA molecules that do not code for protein. The thaumatin protein I consists of a single polypeptide chain of 207 residues.
Like other PR proteins, thaumatin is predicted to have a mainly beta structure, with a high content of beta-turns and little helix. Tobacco cells exposed to gradually increased salt concentrations develop a greatly increased tolerance to salt, due to the expression of osmotin, a member of the PR protein family. Wheat plants attacked by barley powdery mildew express a PR protein (PWIR2), which results in resistance against that infection. The similarity between this PR protein and other PR proteins to the maize alpha-amylase/trypsin inhibitor has suggested PR proteins may act as some form of inhibitor.
The thaumatin-like proteins isolated from kiwi fruit or apple appear to have their allergenic properties minimally reduced by gastroduodenal digestive processes, but not by heating.
Read more about this topic: Thaumatin
Famous quotes containing the words biological and/or role:
“Much of the ill-tempered railing against women that has characterized the popular writing of the last two years is a half-hearted attempt to find a way back to a more balanced relationship between our biological selves and the world we have built. So women are scolded both for being mothers and for not being mothers, for wanting to eat their cake and have it too, and for not wanting to eat their cake and have it too.”
—Margaret Mead (1901–1978)
“Women’s battle for financial equality has barely been joined, much less won. Society still traditionally assigns to woman the role of money-handler rather than money-maker, and our assigned specialty is far more likely to be home economics than financial economics.”
—Paula Nelson (b. 1945)