A chimaeric glutamyl:glutaminyl-tRNA synthetase: implications for evolution
IR@IICB: CSIR-Indian Institute of Chemical Biology, Kolkata
View Archive Info| Field | Value | |
| Title |
A chimaeric glutamyl:glutaminyl-tRNA synthetase: implications
for evolution
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| Creator |
Saha, Rajesh
Dasgupta, Saumya Basu, Gautam Roy, Siddhartha |
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| Subject |
Structural Biology & Bioinformatics
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| Description |
aaRSs (aminoacyl-tRNA synthetases) are multi-domain proteins
that have evolved by domain acquisition. The anti-codon binding
domain was added to the more ancient catalytic domain
during aaRS evolution. Unlike in eukaryotes, the anti-codon
binding domains of GluRS (glutamyl-tRNA synthetase) and
GlnRS (glutaminyl-tRNA synthetase) in bacteria are structurally
distinct. This originates from the unique evolutionary history
of GlnRSs. Starting from the catalytic domain, eukaryotic
GluRS evolved by acquiring the archaea/eukaryote-specific anticodon
binding domain after branching away from the eubacteria
family. Subsequently, eukaryotic GlnRS evolved from GluRS
by gene duplication and horizontally transferred to bacteria. In
order to study the properties of the putative ancestral GluRS
in eukaryotes, formed immediately after acquiring the anticodon
binding domain, we have designed and constructed
a chimaeric protein, cGluGlnRS, consisting of the catalytic
domain, Ec GluRS (Escherichia coli GluRS), and the anticodon
binding domain of EcGlnRS (E. coli GlnRS). In contrast to the isolated EcN-GluRS, cGluGlnRS showed detectable
activity of glutamylation of E. coli tRNAglu and was capable of
complementing an E. coli ts (temperature-sensitive)-GluRS strain
at non-permissive temperatures. Both cGluGlnRS and EcNGluRS
were found to bind E. coli tRNAglu with native EcGluRSlike
affinity, suggesting that the anticodon-binding domain in
cGluGlnRS enhances kcat for glutamylation. This was further
confirmed from similar experiments with a chimaera between
EcN-GluRS and the substrate-binding domain of EcDnaK
(E. coli DnaK). We also show that an extended loop, present in
the anticodon-binding domains of GlnRSs, is absent in archaeal
GluRS, suggesting that the loop was a later addition, generating
additional anti-codon discrimination capability in GlnRS as it
evolved from GluRS in eukaryotes.
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| Date |
2009
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| Type |
Article
PeerReviewed |
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| Format |
application/pdf
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| Identifier |
http://www.eprints.iicb.res.in/135/1/BIOCHEMICAL_JOURNAL%2C417%2C_449%2D455%2C2009[119].pdf
Saha, Rajesh and Dasgupta, Saumya and Basu, Gautam and Roy, Siddhartha (2009) A chimaeric glutamyl:glutaminyl-tRNA synthetase: implications for evolution. Biochem Journal, 417. pp. 449-455. |
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| Relation |
http://dx.doi.org/10.1042/BJ20080747
http://www.eprints.iicb.res.in/135/ |
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