2ZH8: Complex Structure Of Afcca With Trnaminidgc

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.
PDB ID: 2ZH8Download
MMDB ID: 65858
PDB Deposition Date: 2008/2/1
Updated in MMDB: 2011/10
Experimental Method:
x-ray diffraction
Resolution: 2.65  Å
Source Organism:
Archaeoglobus fulgidus
Similar Structures:
Biological Unit for 2ZH8: dimeric; determined by author and by software (PISA)
Molecular Components in 2ZH8
Label Count Molecule
Protein (1 molecule)
Cca-adding Enzyme(Gene symbol: AF_RS10845)
Molecule annotation
Nucleotide(1 molecule)
tRNA (34-mer)
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB