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Multiple effects of L-leucine in Escherichia coli lead to L-leucine sensitive growth in the absence of dephospho-PtsN
  • Neeraj Kumar,
  • Abhijit Sardesai
Neeraj Kumar
Centre for DNA Fingerprinting and Diagnostics
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Abhijit Sardesai
Centre for DNA Fingerprinting and Diagnostics

Corresponding Author:abhijit@cdfd.org.in

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Abstract

In E. coli K-12, absence of dephospho-PtsN, is thought to cause an L-leucine sensitive growth phenotype (LeuS) by hyperactivated K+ uptake mediated impairment of the expression of the ilvBN operon, encoding subunits of the L-valine (Val) sensitive acetohyrodxyacid synthase I (AHAS I), that renders residual AHAS activity susceptible to inhibition by Leu and K+.  This is thought to lead to AHAS insufficiency and a requirement for isoleucine (Ile). Herein we provide an alternate mechanism for LeuS of the ∆ptsN mutant. Genetic and physiological studies with suppressors of the LeuS, indicate that impaired expression of the ilvBN operon jointly caused by the absence of dephospho-PtsN and the presence of Leu coupled to Leu mediated repression of expression of AHAS III leads to AHAS insufficiency rendering residual AHAS activity susceptible to chronic Val stress that may be generated by exogenous Leu. Hyperactivated K+ uptake and an elevated α-ketobutyrate level, mediate elevation of ilvBN expression, and alleviate the LeuS. The requirement of dephospho-PtsN as a positive regulator of ilvBN expression, may buffer Ile biosynthesis against Leu mediated AHAS insufficiency and protect AHAS I function from chronic endogenous Val generated by Leu and could be realised in certain environments that impair AHAS function.
Submitted to Molecular Microbiology
03 Apr 2024Submission Checks Completed
03 Apr 2024Assigned to Editor
04 Apr 2024Reviewer(s) Assigned
24 Apr 2024Review(s) Completed, Editorial Evaluation Pending
01 Jul 20241st Revision Received
05 Aug 2024Review(s) Completed, Editorial Evaluation Pending
05 Aug 2024Editorial Decision: Revise Minor
12 Aug 20242nd Revision Received
13 Aug 2024Submission Checks Completed
13 Aug 2024Assigned to Editor
31 Aug 2024Editorial Decision: Accept