Mutational Analysis Supports Three-Hairpin Model of Attenuator for Transcription Regulation of C Operon in

Overview

Journal Microorganisms

Specialty Microbiology

Date 2025 Feb 26

PMID 40005659

Authors

Ludmila E Ryabchenko

Igor I Titov

Tatyana E Leonova

Tatyana I Kalinina

Tatyana V Gerasimova

Marina E Sheremetieva

Nikolay A Kolchanov

Tamara M Khlebodarova

Alexander S Yanenko

Affiliations

Soon will be listed here.

Abstract

The operon in encodes key enzymes for the biosynthesis of branched-chain amino acids (L-isoleucine, L-leucine, and L-valine). This operon has been studied for quite a long time, and it is assumed that three hairpin mRNA structures can be formed in its regulatory region; however, their functionality and role in the attenuation mechanism of the operon are not completely clear. In the present work, we performed a mutational analysis of mRNA secondary structures in the regulatory region of the operon, which allowed us to propose a model of the regulation of its transcription involving three mRNA hairpins that essentially act as a transcription terminator, an antiterminator, and an antiantiterminator. In this work, we proved the existence of a transcription terminator in this operon and experimentally confirmed the effectiveness of its influence on the expression of the operon, AHAS enzyme activity, and valine production. We demonstrated the unique functional features of this attenuator, which, due to the overlapping of the terminator and antiterminator hairpins, is capable of rapid low-energy transitions between them without the complete disruption of the hairpin structures.

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