Structure/function Correlations in P. aeruginosa DNA Ligase LigD

Abstract

The ATP-dependent DNA ligase D (LigD) performs a major role in non-homologous end-joining (NHEJ) pathway. Pseudomonas aeruginosa LigD (PaeLigD) contains a N-terminal phosphoesterase domain (PE) domain followed by a ligase domain and a C-terminal polymerase domain. The PE domain (187 residues) possesses manganese dependent phosphodiesterase and phosphomonoesterase activities as it sequentially removes the 3′-ribonucleoside from the primer strand of the RNA primer-DNA template duplex and subsequently hydrolyzes the 3′-PO4 to a 3′-OH group (1).PaeLigD-PE belongs to a class of unique 3′- end-processing enzymes as it cleaves the primer strand to a point at which a single ligatable ribonucleotide remains (2).Extensive mutagenesis studies have identified critical residues required for ribonuclease and 3′-phosphatase activities (1). Multiple active sites present in the enzyme lead to the belief that this enzyme possesses some unique motifs. However, in the absence of atomic level structural information clear structure/function correlations are lacking. We are currently working towards obtaining a high-resolution structure of PaeLigD-PE using solution NMR methods.Reference:1) Zhu, H., and Shuman, S. (2006) J. Biol. Chem. 281, 13873-13881.2) Zhu, H., and Shuman, S. (2008) J. Biol. Chem. 283, 8331-8339.