Abstract
DNA processing chain A (DprA) is a DNA-binding protein that is ubiquitous in bacteria and expressed in some archaea. DprA is active in many bacterial species that are competent for transformation of DNA, but its role in Neisseriameningitidis (Nm) is not well characterized. An Nm mutant lacking DprA was constructed, and the phenotypes of the wild-type and ΔdprA mutant were compared. The salient feature of the phenotype of dprA null cells is the total lack of competence for genetic transformation shown by all of the donor DNA substrates tested in this study. Here, Nm wild-type and dprA null cells appeared to be equally resistant to genotoxic stress. The gene encoding DprANm was cloned and overexpressed, and the biological activities of DprANm were further investigated. DprANm binds ssDNA more strongly than dsDNA, but lacks DNA uptake sequence-specific DNA binding. DprANm dimerization and interaction with the C-terminal part of the single-stranded binding protein SSBNmwere demonstrated. dprA is co-expressed with smg, a downstream gene of unknown function, and the gene encoding topoisomerase 1, topA.
Highlights
Neisseria meningitidis (Nm) is a human commensal and pathogen; in the absence of bactericidal antibodies it can cause meningitis and/or septicaemia [1]
The requirement for a functional dprA locus for transformation has been demonstrated in Nm [10] as well as in Neisseria gonorrhoeae (Ng) [17]
To test the role of DprANm in transformation with different DNA substrate conformations, wild-type and dprA null mutant cells were transformed with circular plasmid DNA, chromosomal DNA or PCR-amplified linear chromosomal DNA, all containing an identical pilG :: kan insert
Summary
Neisseria meningitidis (Nm) is a human commensal and pathogen; in the absence of bactericidal antibodies it can cause meningitis and/or septicaemia [1]. The Tfp biogenesis proteins are highly conserved and are required for DNA uptake by most bacterial species that are competent for transformation [7,8,9,10]. In Nm, a dprA null mutant strain displayed >100-fold reduction of transformation with an unspecified substrate type, as compared to wild-type [11]. Apart from this observation, Nm DprA (DprANm) has not previously been characterized. In Bacillus subtilis DprA (DprABs) appears to increase the efficiency of RecA strand exchange during transformation and form a large multiprotein complex with RecA, SSB-B and RMP, recombination mediator protein; SAM, sterile alpha motif; SEC-MALS, size-exclusion chromatography with inline multi-angle light scattering; SSB, single-stranded binding protein; Tfp, type 4 pili. Eleven supplementary figures and four supplementary tables are available with the online Supplementary Material
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