Structure of a ricin mutant showing rescue of activity by a noncatalytic residue

Youngsoo Kim, Debra Mlsna, Arthur F. Monzingo, Michael P. Ready, Art Frankel, Jon D. Robertus

Research output: Contribution to journalArticle

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Abstract

Ricin A chain is an N-glycosidase which removes a single adenine base from a conservative loop of 28S rRNA, thereby inactivating eukaryotic ribosomes. The mechanism of action has been proposed to include transition-state stabilization of an oxycarbonium ion on the substrate ribose by interaction with Glu 177. Conversion of Glu 177 to Gln reduces activity nearly 200-fold [Ready, M. P., Kim, Y., & Robertus, J. D. (1991) Proteins: Struct., Funct., Genet. 10, 270-278] while conversion to Ala (E177A) reduces activity only 20-fold [Schlossman, D., Withers, D., Welsh, P., Alexander, A., Robertus, J., & Frankel, A. (1989) Mol. Cell. Biol. 9, 5012-5021]. X-ray analysis of the latter mutant protein shows that a residue at the edge of the active site, Glu 208, rotates into the space left vacant by the mutation. Its rearranged carboxylate partially substitutes for that of Glu 177. This is equivalent to the rescue of enzyme activity by a second-site reversion. Kinetic analysis shows the E177A mutation affects kcat and not Km, consistent with the notion that the carboxylate serves in transition-state stabilization.

Original languageEnglish (US)
Pages (from-to)3294-3296
Number of pages3
JournalBiochemistry
Volume31
Issue number12
StatePublished - 1992

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Ricin
Stabilization
Viverridae
Enzyme kinetics
Mutation
Ribose
Glycoside Hydrolases
X ray analysis
Enzyme activity
Adenine
Mutant Proteins
Ribosomes
Catalytic Domain
X-Rays
Ions
Substrates
Enzymes
Proteins

ASJC Scopus subject areas

  • Biochemistry

Cite this

Kim, Y., Mlsna, D., Monzingo, A. F., Ready, M. P., Frankel, A., & Robertus, J. D. (1992). Structure of a ricin mutant showing rescue of activity by a noncatalytic residue. Biochemistry, 31(12), 3294-3296.

Structure of a ricin mutant showing rescue of activity by a noncatalytic residue. / Kim, Youngsoo; Mlsna, Debra; Monzingo, Arthur F.; Ready, Michael P.; Frankel, Art; Robertus, Jon D.

In: Biochemistry, Vol. 31, No. 12, 1992, p. 3294-3296.

Research output: Contribution to journalArticle

Kim, Y, Mlsna, D, Monzingo, AF, Ready, MP, Frankel, A & Robertus, JD 1992, 'Structure of a ricin mutant showing rescue of activity by a noncatalytic residue', Biochemistry, vol. 31, no. 12, pp. 3294-3296.
Kim Y, Mlsna D, Monzingo AF, Ready MP, Frankel A, Robertus JD. Structure of a ricin mutant showing rescue of activity by a noncatalytic residue. Biochemistry. 1992;31(12):3294-3296.
Kim, Youngsoo ; Mlsna, Debra ; Monzingo, Arthur F. ; Ready, Michael P. ; Frankel, Art ; Robertus, Jon D. / Structure of a ricin mutant showing rescue of activity by a noncatalytic residue. In: Biochemistry. 1992 ; Vol. 31, No. 12. pp. 3294-3296.
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