ROLES OF THE RELA+ GENE AND OF 4-THIOURIDINE IN NEAR-ULTRAVIOLET (334 nm) RADIATION INHIBITION OF INDUCED SYNTHESIS OF TRYPTOPHANASE IN ESCHERICHIA COLI B/r |
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Authors: | R C Sharma R J Wingo J Jagger † |
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Institution: | Biology Programs, The University of Texas at Dallas, P.O. Box 688, Richardson, TX 75080, USA |
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Abstract: | Abstract— Near-ultraviolet radiation (near UV; 300–380 nm) is known to inhibit the induced synthesis of tryptophanase by tryptophan in Escherichia coli , showing an action spectrum similar to that for near-UV-induced growth delay. The present work shows that a rel A mutant of E. coli B/r exhibits 50% as much monochromatic near-UV (334 nm) inhibition of tryptophanase induction as the wild type, and that a mutant lacking 4-thiouridine, an unusual nucleoside in tRNA, exhibits < 10% as much inhibition of tryptophanase induction. These findings indicate that 4-thiouridine is almost the sole chromophore for this effect in E. coli B/r, but that only 50% of the effect operates by a mechanism utilizing the rel A + gene product; growth delay appears not to be primarily involved. |
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