Inactivation of the Lactobacillus leichmannii ribonucleoside triphosphate reductase by 2'-chloro-2'-deoxyuridine 5'-triphosphate: stoichiometry of inactivation, site of inactivation, and mechanism of the protein chromophore formation

Journal Article · Tue Jun 14 00:00:00 EDT 1988 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00412a017· OSTI ID:7163842

Ashley, G W; Harris, G; Stubbe, J A

The ribonucleoside triphosphate reductase (RTPR) of Lactobacillus leichmannii is inactivated by the substrate analogue 2'-chloro-2'-deoxyuridine 5'-triphosphate (ClUTP). Inactivation is due to alkylation by 2-methylene-3(2H)-furanone, a decomposition product of the enzymic product 3'-keto-2'-deoxyuridine triphosphate. The former has been unambiguously identified as 2-((ethylthio)methyl)-3(2H)-furanone, an ethanethiol trapped adduct, which is identical by /sup 1/H NMR spectroscopy with material synthesized chemically. Subsequent to rapid inactivation, a slow process occurs that results in formation of a new protein-associated chromophore absorbing maximally near 320 nm. The terminal stages of the inactivation have now been investigated in detail. The alkylation and inactivation stoichiometries were studied as a function of the ratio of ClUTP to enzyme. The amount of labeling of RTPR increased with increasing ClUTP concentration up to the maximum of approximately 4 labels/RTPR, yet the degree of inactivation did not increase proportionally. This suggests that (1) RTPR may be inactivated by alkylation of a single site and (2) decomposition of 3'-keto-dUTP is not necessarily enzyme catalyzed. The formation of the new protein chromophore was also monitored during inactivation and found to reach its full extent upon the first alkylation . Thus, out of four alkylation sites, only one appears capable of undergoing the subsequent reaction to form the new chromophore. Model studies suggest that the new chromophore is due to addition of an amino group to the 5-position of enzyme-bound furanone, followed by ring opening and tautomerization to give a ..beta..-aminoenone structure.

• Research Organization: Univ. of Wisconsin, Madison (USA)
• OSTI ID: 7163842
• Journal Information: Biochemistry; (United States), Vol. 27:12
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
59 BASIC BIOLOGICAL SCIENCES
NUCLEOTIDES
STOICHIOMETRY
OXIDOREDUCTASES
INACTIVATION
NUCLEAR MAGNETIC RESONANCE
ALKYLATION
LACTOBACILLUS
PROTONS
TRITIUM COMPOUNDS
UTP
BACTERIA
BARYONS
CHEMICAL REACTIONS
ELEMENTARY PARTICLES
ENZYMES
FERMIONS
HADRONS
LABELLED COMPOUNDS
MAGNETIC RESONANCE
MICROORGANISMS
NUCLEONS
ORGANIC COMPOUNDS
RESONANCE
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