6M9K

Crystal structure of lambda exonuclease in complex with the Red beta C-terminal domain

Summary for 6M9K

• Entry DOI: 10.2210/pdb6m9k/pdb
• Descriptor: Exonuclease, Recombination protein bet, SULFATE ION, ... (4 entities in total)
• Functional Keywords: protein-protein complex, hydrolase
• Biological source: Escherichia phage lambda; More
• Total number of polymer chains: 6
• Total formula weight: 101929.54

Authors

Bell, C.E.,Caldwell, B.J. (deposition date: 2018-08-23, release date: 2019-01-02, Last modification date: 2023-10-11)

Primary citation

Caldwell, B.J.,Zakharova, E.,Filsinger, G.T.,Wannier, T.M.,Hempfling, J.P.,Chun-Der, L.,Pei, D.,Church, G.M.,Bell, C.E.
Crystal structure of the Red beta C-terminal domain in complex with lambda Exonuclease reveals an unexpected homology with lambda Orf and an interaction with Escherichia coli single stranded DNA binding protein.
Nucleic Acids Res., 47:1950-1963, 2019

PubMed Abstract: Bacteriophage λ encodes a DNA recombination system that includes a 5'-3' exonuclease (λ Exo) and a single strand annealing protein (Redβ). The two proteins form a complex that is thought to mediate loading of Redβ directly onto the single-stranded 3'-overhang generated by λ Exo. Here, we present a 2.3 Å crystal structure of the λ Exo trimer bound to three copies of the Redβ C-terminal domain (CTD). Mutation of residues at the hydrophobic core of the interface disrupts complex formation in vitro and impairs recombination in vivo. The Redβ CTD forms a three-helix bundle with unexpected structural homology to phage λ Orf, a protein that binds to E. coli single-stranded DNA binding protein (SSB) to function as a recombination mediator. Based on this relationship, we found that Redβ binds to full-length SSB, and to a peptide corresponding to its nine C-terminal residues, in an interaction that requires the CTD. These results suggest a dual role of the CTD, first in binding to λ Exo to facilitate loading of Redβ directly onto the initial single-stranded DNA (ssDNA) at a 3'-overhang, and second in binding to SSB to facilitate annealing of the overhang to SSB-coated ssDNA at the replication fork.

PubMed: 30624736
DOI: 10.1093/nar/gky1309

Experimental method

X-RAY DIFFRACTION (2.3 Å)