PT  - JOURNAL ARTICLE
AU  - Santosh Kumar Kuncha
AU  - Katta Suma
AU  - Komal Ishwar Pawar
AU  - Jotin Gogoi
AU  - Satya Brata Routh
AU  - Sambhavi Pottabathini
AU  - Shobha P Kruparani
AU  - Rajan Sankaranarayanan
TI  - A discriminator code-based DTD surveillance ensures faithful glycine delivery for protein biosynthesis in bacteria
AID  - 10.1101/322289
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 322289
4099  - http://biorxiv.org/content/early/2018/05/14/322289.short
4100  - http://biorxiv.org/content/early/2018/05/14/322289.full
AB  - D-aminoacyl-tRNA deacylase (DTD) acts on achiral glycine, in addition to D-amino acids, attached to tRNA. We have recently shown that this activity enables DTD to clear non-cognate Gly-tRNAAla with 1000-fold higher efficiency than its activity on Gly-tRNAGly, indicating tRNA-based modulation of DTD (Pawar et al., 2017). Here, we show that tRNA’s discriminator base predominantly accounts for this activity difference and is the key to selection by DTD. Accordingly, the uracil discriminator base, serving as a negative determinant, prevents Gly-tRNAGly misediting by DTD and this protection is augmented by EF-Tu. Intriguingly, eukaryotic DTD has inverted discriminator base specificity and uses only G3•U70 for tRNAGly/Ala discrimination. Moreover, DTD prevents alanine-to-glycine misincorporation in proteins rather than only recycling mischarged tRNAAla. Overall, the study reveals the unique co-evolution of DTD and discriminator base, “reciprocally” in Bacteria and Eukarya, and suggests DTD’s strong selection pressure on bacterial tRNAGlys to retain a pyrimidine discriminator code.