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| {{STRUCTURE_1ou5| PDB=1ou5 | SCENE= }} | | {{STRUCTURE_1ou5| PDB=1ou5 | SCENE= }} |
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| '''Crystal structure of human CCA-adding enzyme'''
| | ===Crystal structure of human CCA-adding enzyme=== |
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| ==Overview==
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| 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.
| | The line below this paragraph, {{ABSTRACT_PUBMED_12729736}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 12729736 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_12729736}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Polymerase]] | | [[Category: Polymerase]] |
| [[Category: Trna]] | | [[Category: Trna]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 04:17:04 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 05:10:01 2008'' |
