4k4h
From Proteopedia
Ternary crystal structures of a human DNA POLYMERASE LAMBDA IN COMPLEX WITH DNA AND (-)3TC-TP.
Structural highlights
Function[DPOLL_HUMAN] Repair polymerase. Involved in base excision repair (BER) responsible for repair of lesions that give rise to abasic (AP) sites in DNA. Has both DNA polymerase and terminal transferase activities. Has a 5'-deoxyribose-5-phosphate lyase (dRP lyase) activity.[1] [2] Publication Abstract from PubMedAlthough lamivudine and emtricitabine, two L-deoxycytidine analogs, have been widely used as antiviral drugs for years, a structural basis for D-stereoselectivity against L-dNTPs, enantiomers of natural nucleotides (D-dNTPs), by any DNA polymerase or reverse transcriptase has not been established due to lack of a ternary structure of a polymerase, DNA, and an incoming L-dNTP. Here, we report 2.10-2.25 A ternary crystal structures of human DNA polymerase lambda, DNA, and L-deoxycytidine 5'-triphosphate (L-dCTP), or the triphosphates of lamivudine ((-)3TC-TP) and emtricitabine ((-)FTC-TP) with four ternary complexes per asymmetric unit. The structures of these 12 ternary complexes reveal that relative to D-deoxycytidine 5'-triphosphate (D-dCTP) in the canonical ternary structure of Pollambda-DNA-D-dCTP, L-dCTP, (-)3TC-TP, and (-)FTC-TP all have their ribose rotated by 180 degrees . Among the four ternary complexes with a specific L-nucleotide, two are similar and show that the L-nucleotide forms three Watson-Crick hydrogen bonds with the templating nucleotide dG and adopts a chair-like triphosphate conformation. In the remaining two similar ternary complexes, the L-nucleotide surprisingly interacts with the side chain of a conserved active site residue R517 through one or two hydrogen bonds, whereas the templating dG is anchored by a hydrogen bond with the side chain of a semiconserved residue Y505. Furthermore, the triphosphate of the L-nucleotide adopts an unprecedented N-shaped conformation. Our mutagenic and kinetic studies further demonstrate that the side chain of R517 is critical for the formation of the abovementioned four complexes along proposed catalytic pathways for L-nucleotide incorporation and provide the structural basis for the D-stereoselectivity of a DNA polymerase. Structural basis for the binding and incorporation of nucleotide analogs with L-stereochemistry by human DNA polymerase lambda,Vyas R, Zahurancik WJ, Suo Z Proc Natl Acad Sci U S A. 2014 Jul 11. pii: 201401286. PMID:25015085[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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