Structure of bacteriophage T4 RNase H, a 5' to 3' RNA-DNA and DNA-DNA exonuclease with sequence similarity to the RAD2 family of eukaryotic proteins

Article Abstract:

Crystal structure studies of bacteriophage T4 RNase H in the presence of Mg2+ and absence of nucleic acids reveal the presence of a central groove similar to that present in DNA-metabolizing enzymes and DNA-binding proteins. The groove divides a large subdomain on the right and a small subdomain on the left. Two magnesium ions are bound in a cluster of conserved acidic residues at the base of the groove to form the active site. The structure of the enzyme furnishes a basis for understanding the structures of other RAD2 nuclease family proteins.

Exonucleases, Bacteriophage T4

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A novel divalent cation-binding site in the A domain of the beta-2 integrin CR3 (CD11b/CD18) is essential for ligand binding

Article Abstract:

The identification of recombinant peptide CD11b, a novel cation-binding site in the A-domain of the beta-2 integrin complement receptor type 3 (CR3), is reported. The peptide bound Mn2+ with high affinity. Other divalent cations competed effectively for Mn2+ binding, while amino acid substitutions at specific sites removed Mn2+ binding properties. These results indicate a previously unknown metal-binding site in the A domain of CR3, and suggest a potential direction for designer drugs against CR3-mediated inflammatory reactions.

Cell receptors, Structure-activity relationships (Biochemistry)

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Crystal structure of the A Domain from the alpha subunit of integrin CR3 (CD11b/CD18)

Article Abstract:

A crystallographic evaluation of the A domain of CR3 integrin helps study its preferential adhesive interactions at the molecular level. A classic alpha/beta Rossmann fold characterizes the domain, which has a Mg2+ coordination site at its surface. The glutamate side chain from another A domain molecule forms a coordinating ligand at this site, which forms the general metal ion-dependent adhesion site (MIDAS) for protein ligand binding. A MIDAS motif inside an altered A domain characterizes the beta subunits of integrins.

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