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| [[Image:1i39.jpg|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_1i39| PDB=1i39 | SCENE= }} | | {{STRUCTURE_1i39| PDB=1i39 | SCENE= }} |
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| '''RNASE HII FROM ARCHAEOGLOBUS FULGIDUS'''
| | ===RNASE HII FROM ARCHAEOGLOBUS FULGIDUS=== |
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| ==Overview==
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| DNA replication and cellular survival requires efficient removal of RNA primers during lagging strand DNA synthesis. In eukaryotes, RNA primer removal is initiated by type 2 RNase H, which specifically cleaves the RNA portion of an RNA-DNA/DNA hybrid duplex. This conserved type 2 RNase H family of replicative enzymes shares little sequence similarity with the well-characterized prokaryotic type 1 RNase H enzymes, yet both possess similar enzymatic properties. Crystal structures and structure-based mutational analysis of RNase HII from Archaeoglobus fulgidus, both with and without a bound metal ion, identify the active site for type 2 RNase H enzymes that provides the general nuclease activity necessary for catalysis. The two-domain architecture of type 2 RNase H creates a positively charged binding groove and links the unique C-terminal helix-loop-helix cap domain to the active site catalytic domain. This architectural arrangement apparently couples directional A-form duplex binding, by a hydrogen-bonding Arg-Lys phosphate ruler motif, to substrate-discrimination, by a tyrosine finger motif, thereby providing substrate-specific catalytic activity. Combined kinetic and mutational analyses of structurally implicated substrate binding residues validate this binding mode. These structural and mutational results together suggest a molecular mechanism for type 2 RNase H enzymes for the specific recognition and cleavage of RNA in the RNA-DNA junction within hybrid duplexes, which reconciles the broad substrate binding affinity with the catalytic specificity observed in biochemical assays. In combination with a recent independent structural analysis, these results furthermore identify testable molecular hypotheses for the activity and function of the type 2 RNase H family of enzymes, including structural complementarity, substrate-mediated conformational changes and coordination with subsequent FEN-1 activity.
| | The line below this paragraph, {{ABSTRACT_PUBMED_11254381}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 11254381 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_11254381}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Helix-loop-helix]] | | [[Category: Helix-loop-helix]] |
| [[Category: Mixed beta sheet]] | | [[Category: Mixed beta sheet]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 19:31:17 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 10:20:51 2008'' |