1ou5
From Proteopedia
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| , resolution 3.40Å | |||||||
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| Gene: | hMtCCA (Homo sapiens) | ||||||
| Related: | 1MIV, 1MIW, 1MIY
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| Resources: | FirstGlance, OCA, PDBsum, RCSB | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
Crystal structure of human CCA-adding enzyme
Overview
All tRNA molecules carry the invariant sequence CCA at their 3'-terminus for amino acid attachment. The post-transcriptional addition of CCA is carried out by ATP(CTP):tRNA nucleotidyltransferase, also called CCase. This enzyme catalyses a unique template-independent but sequence-specific nucleotide polymerization reaction. In order to reveal the molecular mechanism of this activity, we solved the crystal structure of human CCase by single isomorphous replacement. The structure reveals a four domain architecture with a cluster of conserved residues forming a positively charged cleft between the first two domains. Structural homology of the N-terminal CCase domain to other nucleotidyltransferases could be exploited for modeling a tRNA-substrate complex. The model places the tRNA 3'-end into the N-terminal nucleotidyltransferase site, close to a patch of conserved residues that provide the binding sites for CTP and ATP. Based on our results, we introduce a corkscrew model for CCA addition that includes a fixed active site and a traveling tRNA-binding region formed by flexible parts of the protein.
About this Structure
1OU5 is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.
Reference
Crystal structure of the human CCA-adding enzyme: insights into template-independent polymerization., Augustin MA, Reichert AS, Betat H, Huber R, Morl M, Steegborn C, J Mol Biol. 2003 May 16;328(5):985-94. PMID:12729736
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