1VSF: Asv Integrase Core Domain With Mn(Ii) Cofactor And Hepes Ligand, High Mg Concentration Form

Citation:
Abstract
BACKGROUND: Members of the structurally-related superfamily of enzymes that includes RNase H, RuvC resolvase, MuA transposase, and retroviral integrase require divalent cations for enzymatic activity. So far, cation positions are reported in the X-ray crystal structures of only two of these proteins, E. coli and human immunodeficiency virus 1 (HIV-1) RNase H. Details of the placement of metal ions in the active site of retroviral integrases are necessary for the understanding of the catalytic mechanism of these enzymes. RESULTS: The structure of the enzymatically active catalytic domain (residues 52-207) of avian sarcoma virus integrase (ASV IN) has been solved in the presence of divalent cations (Mn2+ or Mg2+), at 1.7-2.2 A resolution. A single ion of either type interacts with the carboxylate groups of the active site aspartates and uses four water molecules to complete its octahedral coordination. The placement of the aspartate side chains and metal ions is very similar to that observed in the RNase H members of this superfamily; however, the conformation of the catalytic aspartates in the active site of ASV IN differs significantly from that reported for the analogous residues in HIV-1 IN. CONCLUSIONS: Binding of the required metal ions does not lead to significant structural modifications in the active site of the catalytic domain of ASV IN. This indicates that at least one metal-binding site is preformed in the structure, and suggests that the observed constellation of the acidic residues represents a catalytically competent active site. Only a single divalent cation was observed even at extremely high concentrations of the metals. We conclude that either only one metal ion is needed for catalysis, or that a second metal-binding site can only exist in the presence of substrate and/or other domains of the protein. The unexpected differences between the active sites of ASV IN and HIV-1 IN remain unexplained; they may reflect the effects of crystal contacts on the active site of HIV-1 IN, or a tendency for structural polymorphism.
PDB ID: 1VSFDownload
MMDB ID: 57632
PDB Deposition Date: 1995/11/29
Updated in MMDB: 2012/10
Experimental Method:
x-ray diffraction
Resolution: 2.05  Å
Source Organism:
Similar Structures:
Biological Unit for 1VSF: dimeric; determined by author
Molecular Components in 1VSF
Label Count Molecule
Proteins (2 molecules)
2
Integrase
Molecule annotation
Chemicals (4 molecules)
1
2
2
2
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