Relaxed Substrate Specificity Leads to Extensive tRNA Mischarging by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Class I and Class II Aminoacyl-tRNA Synthetases

ABSTRACT Aminoacyl-tRNA synthetases provide the first step in protein synthesis quality control by discriminating cognate from noncognate amino acid and tRNA substrates. While substrate specificity is enhanced in many instances by cis- and trans-editing pathways, it has been revealed that in organis...

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Autores principales:	Jennifer Shepherd, Michael Ibba
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2014
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/b29f60d7c9d942bc9eeb028ae034436b
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spelling	oai:doaj.org-article:b29f60d7c9d942bc9eeb028ae034436b2021-11-15T15:45:54ZRelaxed Substrate Specificity Leads to Extensive tRNA Mischarging by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Class I and Class II Aminoacyl-tRNA Synthetases10.1128/mBio.01656-142150-7511https://doaj.org/article/b29f60d7c9d942bc9eeb028ae034436b2014-10-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01656-14https://doaj.org/toc/2150-7511ABSTRACT Aminoacyl-tRNA synthetases provide the first step in protein synthesis quality control by discriminating cognate from noncognate amino acid and tRNA substrates. While substrate specificity is enhanced in many instances by cis- and trans-editing pathways, it has been revealed that in organisms such as Streptococcus pneumoniae some aminoacyl-tRNA synthetases display significant tRNA mischarging activity. To investigate the extent of tRNA mischarging in this pathogen, the aminoacylation profiles of class I isoleucyl-tRNA synthetase (IleRS) and class II lysyl-tRNA synthetase (LysRS) were determined. Pneumococcal IleRS mischarged tRNAIle with both Val, as demonstrated in other bacteria, and Leu in a tRNA sequence-dependent manner. IleRS substrate specificity was achieved in an editing-independent manner, indicating that tRNA mischarging would only be significant under growth conditions where Ile is depleted. Pneumococcal LysRS was found to misaminoacylate tRNALys with Ala and to a lesser extent Thr and Ser, with mischarging efficiency modulated by the presence of an unusual U4:G69 wobble pair in the acceptor stems of both pneumococcal tRNALys isoacceptors. Addition of the trans-editing factor MurM, which also functions in peptidoglycan synthesis, reduced Ala-tRNALys production by LysRS, providing evidence for cross talk between the protein synthesis and cell wall biogenesis pathways. Mischarging of tRNALys by AlaRS was also observed, and this would provide additional potential MurM substrates. More broadly, the extensive mischarging activities now described for a number of Streptococcus pneumoniae aminoacyl-tRNA synthetases suggest that adaptive misaminoacylation may contribute significantly to the viability of this pathogen during amino acid starvation. IMPORTANCE Streptococcus pneumoniae is a common causative agent of several debilitating and potentially life-threatening infections, such as pneumonia, meningitis, and infectious endocarditis. Such infections are increasingly difficult to treat due to widespread development of penicillin resistance. High-level penicillin resistance is known to depend in part upon MurM, a protein involved in both aminoacyl-tRNA-dependent synthesis of indirect amino acid cross-linkages within cell wall peptidoglycan and in translation quality control. The involvement of MurM in both protein synthesis and antibiotic resistance identify it as a potential target for the development of new and potent antibiotics for pneumococcal infections. The goals of this work were to identify and characterize S. pneumoniae pathways that can synthesize mischarged tRNAs and to relate these activities to expected changes in protein and peptidoglycan biosynthesis during antibiotic and nutritional stress.Jennifer ShepherdMichael IbbaAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 5, Iss 5 (2014)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Jennifer Shepherd Michael Ibba Relaxed Substrate Specificity Leads to Extensive tRNA Mischarging by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Class I and Class II Aminoacyl-tRNA Synthetases
description	ABSTRACT Aminoacyl-tRNA synthetases provide the first step in protein synthesis quality control by discriminating cognate from noncognate amino acid and tRNA substrates. While substrate specificity is enhanced in many instances by cis- and trans-editing pathways, it has been revealed that in organisms such as Streptococcus pneumoniae some aminoacyl-tRNA synthetases display significant tRNA mischarging activity. To investigate the extent of tRNA mischarging in this pathogen, the aminoacylation profiles of class I isoleucyl-tRNA synthetase (IleRS) and class II lysyl-tRNA synthetase (LysRS) were determined. Pneumococcal IleRS mischarged tRNAIle with both Val, as demonstrated in other bacteria, and Leu in a tRNA sequence-dependent manner. IleRS substrate specificity was achieved in an editing-independent manner, indicating that tRNA mischarging would only be significant under growth conditions where Ile is depleted. Pneumococcal LysRS was found to misaminoacylate tRNALys with Ala and to a lesser extent Thr and Ser, with mischarging efficiency modulated by the presence of an unusual U4:G69 wobble pair in the acceptor stems of both pneumococcal tRNALys isoacceptors. Addition of the trans-editing factor MurM, which also functions in peptidoglycan synthesis, reduced Ala-tRNALys production by LysRS, providing evidence for cross talk between the protein synthesis and cell wall biogenesis pathways. Mischarging of tRNALys by AlaRS was also observed, and this would provide additional potential MurM substrates. More broadly, the extensive mischarging activities now described for a number of Streptococcus pneumoniae aminoacyl-tRNA synthetases suggest that adaptive misaminoacylation may contribute significantly to the viability of this pathogen during amino acid starvation. IMPORTANCE Streptococcus pneumoniae is a common causative agent of several debilitating and potentially life-threatening infections, such as pneumonia, meningitis, and infectious endocarditis. Such infections are increasingly difficult to treat due to widespread development of penicillin resistance. High-level penicillin resistance is known to depend in part upon MurM, a protein involved in both aminoacyl-tRNA-dependent synthesis of indirect amino acid cross-linkages within cell wall peptidoglycan and in translation quality control. The involvement of MurM in both protein synthesis and antibiotic resistance identify it as a potential target for the development of new and potent antibiotics for pneumococcal infections. The goals of this work were to identify and characterize S. pneumoniae pathways that can synthesize mischarged tRNAs and to relate these activities to expected changes in protein and peptidoglycan biosynthesis during antibiotic and nutritional stress.
format	article
author	Jennifer Shepherd Michael Ibba
author_facet	Jennifer Shepherd Michael Ibba
author_sort	Jennifer Shepherd
title	Relaxed Substrate Specificity Leads to Extensive tRNA Mischarging by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Class I and Class II Aminoacyl-tRNA Synthetases
title_short	Relaxed Substrate Specificity Leads to Extensive tRNA Mischarging by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Class I and Class II Aminoacyl-tRNA Synthetases
title_full	Relaxed Substrate Specificity Leads to Extensive tRNA Mischarging by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Class I and Class II Aminoacyl-tRNA Synthetases
title_fullStr	Relaxed Substrate Specificity Leads to Extensive tRNA Mischarging by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Class I and Class II Aminoacyl-tRNA Synthetases
title_full_unstemmed	Relaxed Substrate Specificity Leads to Extensive tRNA Mischarging by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Class I and Class II Aminoacyl-tRNA Synthetases
title_sort	relaxed substrate specificity leads to extensive trna mischarging by <named-content content-type="genus-species">streptococcus pneumoniae</named-content> class i and class ii aminoacyl-trna synthetases
publisher	American Society for Microbiology
publishDate	2014
url	https://doaj.org/article/b29f60d7c9d942bc9eeb028ae034436b
work_keys_str_mv	AT jennifershepherd relaxedsubstratespecificityleadstoextensivetrnamischargingbynamedcontentcontenttypegenusspeciesstreptococcuspneumoniaenamedcontentclassiandclassiiaminoacyltrnasynthetases AT michaelibba relaxedsubstratespecificityleadstoextensivetrnamischargingbynamedcontentcontenttypegenusspeciesstreptococcuspneumoniaenamedcontentclassiandclassiiaminoacyltrnasynthetases
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Relaxed Substrate Specificity Leads to Extensive tRNA Mischarging by <named-content content-type="genus-species">Streptococcus pneumoniae</named-content> Class I and Class II Aminoacyl-tRNA Synthetases

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