1ZQO

DNA POLYMERASE BETA (POL B) (E.C.2.7.7.7) COMPLEXED WITH SEVEN BASE PAIRS OF DNA; SOAKED IN THE PRESENCE OF CACL2 (15 MILLIMOLAR) AND NACL (15 MILLIMOLAR)

Summary for 1ZQO

• Entry DOI: 10.2210/pdb1zqo/pdb
• Related: 1ZQA 1ZQB 1ZQC 1ZQD 1ZQE 1ZQF 1ZQG 1ZQH 1ZQI 1ZQJ 1ZQK 1ZQL 1ZQM 1ZQN 1ZQP 1ZQQ 1ZQR 1ZQS 1ZQT 7ICE 7ICF 7ICG 7ICH 7ICI 7ICJ 7ICK 7ICL 7ICM 7ICN 7ICO 7ICP 7ICQ 7ICR 7ICS 7ICT 7ICU 7ICV 8ICA 8ICB 8ICC 8ICE 8ICF 8ICG 8ICH 8ICI 8ICJ 8ICK 8ICL 8ICM 8ICN 8ICO 8ICP 8ICQ 8ICR 8ICS 8ICT 8ICU 8ICV 8ICW 8ICX 8ICY 8ICZ 9ICA 9ICB 9ICC 9ICE 9ICF 9ICG 9ICH 9ICI 9ICJ 9ICK 9ICL 9ICM 9ICN 9ICO 9ICP 9ICQ 9ICR 9ICS 9ICT 9ICU 9ICV 9ICW 9ICX 9ICY
• Descriptor: DNA (5'-D(*CP*AP*TP*TP*AP*GP*AP*A)-3'), DNA (5'-D(*TP*CP*TP*AP*AP*TP*G)-3'), PROTEIN (DNA POLYMERASE BETA (E.C.2.7.7.7)), ... (5 entities in total)
• Functional Keywords: dna-directed dna polymerase, dna replication, dna repair, nucleotidyltransferase, complex (nucleotidyltransferase-dna, transferase-dna complex, transferase/dna
• Biological source: Homo sapiens (human)
• Cellular location: Nucleus: P06746
• Total number of polymer chains: 3
• Total formula weight: 42834.72

Authors

Pelletier, H.,Sawaya, M.R. (deposition date: 1996-04-12, release date: 1996-11-15, Last modification date: 2023-08-02)

Primary citation

Pelletier, H.,Sawaya, M.R.
Characterization of the metal ion binding helix-hairpin-helix motifs in human DNA polymerase beta by X-ray structural analysis.
Biochemistry, 35:12778-12787, 1996

PubMed Abstract: X-ray crystallographic studies have shown that DNA binding by human polymerase beta (pol beta) occurs primarily through two structurally and sequentially homologous helix-hairpin-helix (HhH) motifs, one in the fingers subdomain and the other in the 8-kDa domain [Pelletier, H., Sawaya, M. R., Wolfle, W., Wilson, S. H., & Kraut, J. (1996a) Biochemistry 35, 12742-12761]. In that DNA binding by each HhH motif is facilitated by a metal ion, we set out to determine the identity of the metal ion that most likely binds to the HhH motif in vivo. Crystal soaking experiments were performed on human pol beta-DNA cocrystals with Mg2+, Ca2+, Na+, and K+, the four most prevalent metal ions in the cell, and in each case a data set was collected and the resulting structure was refined. Under the conditions tested, the HhH motifs of pol beta have an affinity for these biologically prevalent metal ions in the order Mg2+ < Ca2+ < Na+ < K+, with K+ displaying the strongest binding. Crystals soaked in the presence of Tl+, a commonly used spectroscopic probe for K+, were too X-ray-sensitive to establish the binding behavior of Tl+, but soaking experiments with Ba2+ and Cs+ resulted in relatively stable crystals that gave evidence of metal ion binding in both HhH motifs, confirming that larger monovalent and divalent metal ions are capable of binding to the HhH metal sites. Although Mn2+, which has been categorized as a potent polymerase mutagen, binds to the HhH motifs with a greater affinity than Mg2+, Mn2+ does not bind to the HhH motifs in the presence of equimolar concentrations of Na+. These results suggest that in vivo, where Mn2+ is present only in trace amounts, Mn2+ probably does not have a large effect on DNA binding and may instead manifest a mutagenic effect on pol beta primarily by distorting nucleotide binding or by directly affecting the catalytic step [Pelletier, H., Sawaya, M. R., Wolfle, W., Wilson, S. H., & Kraut, J. (1996b) Biochemistry 35, 12762-12777]. Crystal soaking experiments with 31-kDa apoenzyme crystals show that, in the absence of DNA, the HhH motif in the fingers subdomain binds metal ions with either much lower occupancy or not at all, indicating that metal ion binding is dependent on the presence of the DNA substrate.

PubMed: 8841120
DOI: 10.1021/bi960790i

Experimental method

X-RAY DIFFRACTION (3.2 Å)