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PDBsum entry 5hjj
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References listed in PDB file
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Key reference
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Title
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Crystal structures of the bifunctional tRNA methyltransferase trm5a.
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Authors
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C.Wang,
Q.Jia,
R.Chen,
Y.Wei,
J.Li,
J.Ma,
W.Xie.
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Ref.
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Sci Rep, 2016,
6,
33553.
[DOI no: ]
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PubMed id
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Abstract
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tRNA methyltransferase Trm5 catalyses the transfer of a methyl group from
S-adenosyl-L-methionine to G37 in eukaryotes and archaea. The N1-methylated
guanosine is the product of the initial step of the wyosine hypermodification,
which is essential for the maintenance of the reading frame during translation.
As a unique member of this enzyme family, Trm5a from Pyrococcus abyssi (PaTrm5a)
catalyses not only the methylation of N1, but also the further methylation of C7
on 4-demethylwyosine at position 37 to produce isowyosine, but the mechanism for
the double methylation is poorly understood. Here we report four crystal
structures of PaTrm5a ranging from 1.7- to 2.3-Å, in the apo form or in complex
with various SAM analogues. These structures reveal that Asp243 specifically
recognises the base moiety of SAM at the active site. Interestingly, the protein
in our structures all displays an extended conformation, quite different from
the well-folded conformation of Trm5b from Methanocaldococcus jannaschii
reported previously, despite their similar overall architectures. To rule out
the possibilities of crystallisation artefacts, we conducted the fluorescence
resonance energy transfer (FRET) experiments. The FRET data suggested that
PaTrm5a adopts a naturally extended conformation in solution, and therefore the
open conformation is a genuine state of PaTrm5a.
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