G673 could be a novel mutational hot spot for intragenic suppressors of pheS5 lesion in Escherichia coli. Issue 3 (8th May 2014)

• Record Type: Journal Article
• Authors: Ponmani, Thangaraj; Munavar, M. Hussain
• Is Part Of: MicrobiologyOpen. Volume 3:Issue 3(2014:Jun.)
• Page Start: 369
• Page End: 382
• Publication Date: 2014-05-08
• Subjects: Microbiology -- Periodicals; 579
• DOI: 10.1002/mbo3.161
• Languages: English
• ISSNs: 2045-8827

Abstract

<abstract abstract-type="main" id="mbo3161-abs-0001"> <title>Abstract</title> <p>The <italic>pheS5</italic> Ts mutant of <italic>Escherichia coli</italic> defined by a G<sub>293</sub> → A<sub>293</sub> transition, which is responsible for thermosensitive Phenylalanyl‐tRNA synthetase has been well studied at both biochemical and molecular level but genetic analyses pertaining to suppressors of <italic>pheS5</italic> were hard to come by. Here we have systematically analyzed a spectrum of Temperature‐insensitive derivatives isolated from <italic>pheS5</italic> Ts mutant and identified two intragenic suppressors affecting the same base pair coordinate G<sub>673</sub> (<italic>pheS19</italic> defines G<sub>673</sub> → T<sub>673</sub>; Gly<sub>225</sub> → Cys<sub>225</sub> and <italic>pheS28</italic> defines G<sub>673</sub> → C<sub>673</sub>; Gly<sub>225</sub> → Arg<sub>225</sub>). In fact in the third derivative, the intragenic suppressor originally named <italic>pheS43</italic> (G<sub>673</sub> → C<sub>673</sub>transversion) is virtually same as <italic>pheS28</italic>. In the fourth case, the very <italic>pheS5</italic> lesion itself has got changed from A<sub>293</sub> → T<sub>293</sub> (named <italic>pheS40</italic>). Cloning of <italic>pheS</italic><sup><italic>+</italic></sup>, <italic>pheS5</italic>, <italic> pheS5‐pheS19, pheS5‐pheS28</italic> alleles into pBR322 and introduction of these clones into <italic>pheS5</italic> mutant revealed that excess of double mutant protein is not at all good for the survival of cells at 42°C. These results clearly indicate a pivotal role for Gly<sub>225</sub> in the structural/functional integrity of alpha subunit of <italic>E. coli</italic> PheRS enzyme and it is proposed that G<sub>673</sub> might define a hot spot for intragenic suppressors of <italic>pheS5</italic>.</p> </abstract>