title: Inhibition of sulfur incorporation to transfer RNA by ultraviolet-A radiation in Escherichia coli.
abstract: tRNA sulfurtransferase activity was assayed in Escherichia coli cell extracts obtained from bacterial suspensions exposed to a sub-lethal dose of ultraviolet-A radiation (fluence 148 kJ m(-2)) imparted at a low fluence rate (41 W m(-2)). We found that the irradiation reduced the enzymatic activity to one fourth of the control value, indicating that ultraviolet-A exposure inhibits the synthesis of 4-thiouridine, the most abundant thionucleoside in E. coli tRNA. Changes in the tRNA content of 4-thiouridine and its derived photoproduct 5-(4'-pyrimidin 2'-one) cytosine were studied in bacteria growing under ultraviolet-A irradiation. In these conditions the accumulation of photoproduct was limited, and the kinetics of this process was non-coincident with disappearance of 4-thiouridine. The results, which are compatible with the fact that ultraviolet-A induces an inhibition of the 4-thiouridine synthesis, suggest that the effect of radiation on tRNA modification is relevant to tRNA photo-inactivation in growing bacteria.
authors.affiliation: Departamento de Radiobiología, Comisión Nacional de Energía Atómica, Av. General Paz 1499, 1650 General San Martín, Buenos Aires, Argentina. oppezzo@cnea.gov.ar
authors.forename: Oscar J
authors.initials: OJ
authors.lastname: Oppezzo
authors.forename: Ramón A
authors.initials: RA
authors.lastname: Pizarro
mesh_terms: D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000528:radiation effects*; D007700:Kinetics; D012329:RNA, Bacterial / Q000378:metabolism / Q000528:radiation effects*; D012343:RNA, Transfer / Q000378:metabolism / Q000528:radiation effects*; D013455:Sulfur / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013466:Sulfurtransferases / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D012329:RNA, Bacterial; D013455:Sulfur; D012343:RNA, Transfer; D013466:Sulfurtransferases; C023200:tRNA sulfurtransferase