Purification and structural analysis of an abundant thaumatin-like protein from ripe banana fruit

Abstract

The pulp of ripe bananas (Musa acuminata) contains an abundant thaumatin-like protein (TLP). Characterization of the protein and molecular cloning of the corresponding gene from banana demonstrated that the native protein consists of a single polypeptide chain of 200 amino acid residues. Molecular modelling further revealed that the banana thaumatin-like protein (Ban-TLP) adopts an overall fold similar to that of thaumatin and thaumatin-like PR-5 proteins. Although the banana protein exhibits an electrostatically polarized surface, which is believed to be essential for the antifungal properties of TLPs, it is apparently devoid of antifungal activity towards pathogenic fungi. It exhibits a low but detectable in vitro endo-beta-1,3-glucanase (EC 3.2.1.x) activity. As well as being present in fruits, Ban-TLP also occurs in root tips where its accumulation is enhanced by methyl jasmonate treatment of plants. Pulp of plantains (Musa acuminata) also contains a very similar TLP, which is even more abundant than its banana homologue. Our results demonstrate for the first time that fruit-specific (abundant) TLPs are not confined to dicots but occur also in fruits of monocot species. The possible role of the apparent widespread accumulation of fruit-specific TLPs is discussed.

Molecular, biochemical and structural characterization of osmotin-like protein from black nightshade (Solanum nigrum)

“…This can be attributed due to the presence of E71 and E150 amino acids located at the top of an extended cleft region unlike in endoglucanases in which, they occur in the center of the cleft and extends across the surface of the enzyme. The TLP from banana (BanTLP) showed a weak antifungal activity without any enzymatic activity probably due to the improper positioning of glutamate residues with the linear glucan (Barre et al, 2000). The same reason can be corroborated to recombinant SniOLP protein that also lacked endoglucanase-like activity.…”

“…After stirring, the solutions were filtered through a Whatmann no. 1 paper and their absorbance measured at 590 nm against a substrate blank without protein and similarly incubated at 30 1C for 1, 2 and 3 d. The increase in absorbance at 590 nm shows the endo-b-1,3-glucanase activity (Barre et al, 2000).…”

Household uses of the banana plant in eastern Democratic Republic of Congo

“…Furthermore, the pith or the tender core of the banana pseudostem (un-emerged immature leaves) has been used as food after boiling and the addition of spices (Mohapatra et al, 2010). In terms of medicinal properties, the banana pseudostem contains pathogenesis-proteins possessing antimicrobial properties (Baree et al, 2000). In addition, banana pseudostem fibre bundles have high specific strength modulus (Lassoudière, 2010); therefore, some automobile companies use this fibre to reinforce the body of the vehicle (Pothan et al, 2005).…”

Biochemical, molecular and structural analysis of multiple thaumatin-like proteins from the elderberry tree ( Sambucus nigra L.)

“…However, the role of the acidic cleft in the antifungal properties of PR-5 proteins remains controversial because the TLP from elderberry fruits possesses an acidic cleft but is apparently devoid of antifungal activity. A similar observation was made for the banana TLP, which, in spite of the presence of an acidic cleft, has no antifungal activity (Barre et al 2000).…”