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PDBsum entry 2zh6
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Transferase/RNA
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PDB id
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2zh6
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References listed in PDB file
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Key reference
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Title
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Molecular basis for maintenance of fidelity during the cca-Adding reaction by a cca-Adding enzyme.
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Authors
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Y.Toh,
T.Numata,
K.Watanabe,
D.Takeshita,
O.Nureki,
K.Tomita.
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Ref.
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Embo J, 2008,
27,
1944-1952.
[DOI no: ]
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PubMed id
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Abstract
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CCA-adding enzyme builds the 3'-end CCA of tRNA without a nucleic acid template.
The mechanism for the maintenance of fidelity during the CCA-adding reaction
remains elusive. Here, we present almost a dozen complex structures of the class
I CCA-adding enzyme and tRNA mini-helices (mini-D(73)N(74), mini-D(73)N(74)C(75)
and mini-D(73)C(74)N(75); D(73) is a discriminator nucleotide and N is either A,
G, or U). The mini-D(73)N(74) complexes adopt catalytically inactive open forms,
and CTP shifts the enzymes to the active closed forms and allows N(74) to flip
for CMP incorporation. In contrast, unlike the catalytically active closed form
of the mini-D(73)C(74)C(75) complex, the mini-D(73)N(74)C(75) and
mini-D(73)C(74)N(75) complexes adopt inactive open forms. Only the
mini-D(73)C(74)U(75) accepts AMP to a similar extent as mini-D(73)C(74)C(75),
and ATP shifts the enzyme to a closed, active form and allows U(75) to flip for
AMP incorporation. These findings suggest that the 3'-region of RNA is
proofread, after two nucleotide additions, in the closed, active form of the
complex at the AMP incorporation stage. This proofreading is a prerequisite for
the maintenance of fidelity for complete CCA synthesis.
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