Features of the structure of catalytic subunits of toxins, inhibiting protein synthesis. I. The effect of pH and interaction with the B-chain of ricin (Russisch)

Journal/Book: Mol-Biol (Mosk) 25 (2), 422-430. 1991;

Abstract: A comparative study of gelonin and A-chains of ricin, mistletoe lectin Iand diphtheria toxin was undertaken. The effect of pH was studied on: a)the conformation of the proteins under study using intrinsicfluorescence; b) interaction of these proteins with ricin B-chain usinggel-filtration. Structural stability of the proteins was assessedaccording to denaturing action of guanidine hydrochloride andtemperature, and localization of tryptophan residues was determinedusing fluorescence quenching by I-, Cs+ and acrylamide. All investigatedproteins were shown to undergo the conformational changes when aenvironment became acidic. In comparison with an intactprotein--gelonin, the A-chains of ricin, a mistletoe lectin and adiphtheria toxin are less stable. At pH less than 5.0 tryptophanresidues became more accessible to quencher and a positive charge of thesurrounding area increases (in the case of gelonin it is negativelycharged). No reliable interaction of a ricin B-chain with both geloninand A-chain of diphtheria toxin was observed. The interaction of a ricinB-chain with a A-chain of mistletoe lectin I is weaker than that withricin A-chain and is practically pH-independent. Author.

Keyword(s): CATALYSIS

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