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Journal of Bacteriology, March 2008, p. 1937-1945, Vol. 190, No. 6
0021-9193/08/$08.00+0     doi:10.1128/JB.01820-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Physiological Effects of Anti-TRAP Protein Activity and tRNATrp Charging on trp Operon Expression in Bacillus subtilis{triangledown}

Luis R. Cruz-Vera ,{ddagger},{dagger} Ming Gong,§,{dagger} and Charles Yanofsky*

Department of Biological Sciences, Stanford University, Stanford, California 94305-5020

Received 16 November 2007/ Accepted 21 December 2007

The Bacillus subtilis anti-TRAP protein regulates the ability of the tryptophan-activated TRAP protein to bind to trp operon leader RNA and promote transcription termination. AT synthesis is regulated both transcriptionally and translationally by uncharged tRNATrp. In this study, we examined the roles of AT synthesis and tRNATrp charging in mediating physiological responses to tryptophan starvation. Adding excess phenylalanine to wild-type cultures reduced the charged tRNATrp level from 80% to 40%; the charged level decreased further, to 25%, in an AT-deficient mutant. Adding tryptophan with phenylalanine increased the charged tRNATrp level, implying that phenylalanine, when added alone, reduces the availability of tryptophan for tRNATrp charging. Changes in the charged tRNATrp level observed during growth with added phenylalanine were associated with increased transcription of the genes of tryptophan metabolism. Nutritional shift experiments, from a medium containing tryptophan to a medium with phenylalanine and tyrosine, showed that wild-type cultures gradually reduced their charged tRNATrp level. When this shift was performed with an AT-deficient mutant, the charged tRNATrp level decreased even further. Growth rates for wild-type and mutant strains deficient in AT or TRAP or that overproduce AT were compared in various media. A lack of TRAP or overproduction of AT resulted in phenylalanine being required for growth. These findings reveal the importance of AT in maintaining a balance between the synthesis of tryptophan versus the synthesis of phenylalanine, with the level of charged tRNATrp acting as the crucial signal regulating AT production.

* Corresponding author. Mailing address: Department of Biological Sciences, Stanford University, 371 Serra Mall, Stanford, CA 94305. Phone: (650) 725-1835. Fax: (650) 725-8221. E-mail: yanofsky{at}stanford.edu

{triangledown} Published ahead of print on 4 January 2008.

{ddagger} Present address: Department of Biological Sciences, University of Alabama/Huntsville, Huntsville, AL 35899.

{dagger} These authors contributed equally.

§ Present address: Department of Biological Chemistry, UCLA Medical School, Los Angeles, CA 90095.

Journal of Bacteriology, March 2008, p. 1937-1945, Vol. 190, No. 6
0021-9193/08/$08.00+0     doi:10.1128/JB.01820-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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