Open AccessFunctional roles of N‐terminal and C‐terminal domains in the overall activity of a novel single‐stranded DNA binding protein of Deinococcus radiodurans
Author(s) -
Ujaoney Aman K.,
Basu Bhakti,
Muniyappa K.,
Apte Shree K.
Publication year - 2015
Publication title -
febs open bio
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.718
H-Index - 31
ISSN - 2211-5463
DOI - 10.1016/j.fob.2015.04.009
Subject(s) - deinococcus radiodurans , dna , biology , microbiology and biotechnology , oligonucleotide , plasma protein binding , cold shock domain , chemistry , biochemistry , gene , rna
Single‐stranded DNA binding protein (Ssb) of Deinococcus radiodurans comprises N‐ and C‐terminal oligonucleotide/oligosaccharide binding (OB) folds connected by a beta hairpin connector. To assign functional roles to the individual OB folds, we generated three Ssb variants: Ssb N (N‐terminal without connector), Ssb NC (N‐terminal with connector) and Ssb C (C‐terminal), each harboring one OB fold. Both Ssb N and Ssb NC displayed weak single‐stranded DNA (ssDNA) binding activity, compared to the full‐length Ssb (Ssb FL ). The level of ssDNA binding activity displayed by Ssb C was intermediate between Ssb FL and Ssb N . Ssb C and Ssb FL predominantly existed as homo‐dimers while Ssb NC /Ssb N formed different oligomeric forms. In vitro , Ssb NC or Ssb N formed a binary complex with Ssb C that displayed enhanced ssDNA binding activity. Unlike Ssb FL , Ssb variants were able to differentially modulate topoisomerase‐I activity, but failed to stimulate Deinococcal RecA‐promoted DNA strand exchange. The results suggest that the C‐terminal OB fold is primarily responsible for ssDNA binding. The N‐terminal OB fold binds weakly to ssDNA but is involved in multimerization.