Open AccessRings and filaments of β protein from bacteriophage λ suggest a superfamily of recombination proteins
Author(s) -
Sophia I. Passy,
Yong Xiong,
Zhufang Li,
Charles M. Radding,
Edward H. Egelman
Publication year - 1999
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.96.8.4279
Subject(s) - dna , homologous recombination , exonuclease , bacteriophage , biology , replication protein a , protein subunit , genetic recombination , oligonucleotide , rad52 , chemistry , recombination , biochemistry , rad51 , dna binding protein , dna polymerase , gene , escherichia coli , transcription factor
The β protein of bacteriophage λ acts in homologous genetic recombination by catalyzing the annealing of complementary single-stranded DNA produced by the λ exonuclease. It has been shown that the β protein binds to the products of the annealing reaction more tightly than to the initial substrates. We find that β protein exists in three structural states. In the absence of DNA, β protein forms inactive rings with ≈12 subunits. The active form of the β protein in the presence of oligonucleotides or single-stranded DNA is a ring, composed of ≈15–18 subunits. The double-stranded products of the annealing reaction catalyzed by the rings are bound by β protein in a left-handed helical structure, which protects the products from nucleolytic degradation. These observations suggest structural homology for a family of proteins, including the phage P22 erf, the bacterial RecT, and the eukaryotic Rad52 proteins, all of which are involved in homologous recombination.