DNA transformation is a widespread process allowing bacteria to capture free DNA
by using filamentous nano-machines composed of type IV pilins. These proteins can
act as DNA receptors as demonstrated by the finding that Neisseria meningitidis
ComP minor pilin has intrinsic DNA-binding ability. ComP binds DNA better when it
contains the DNA uptake sequence (DUS) motif abundant in this species genome,
playing a role in its trademark ability to selectively take up its own DNA. Here, we
report high-resolution structures for meningococcal ComP and Neisseria subflava
ComPsub, which recognize different DUS motifs. We show that they are structurally
identical type IV pilins that pack readily into filament models and display a unique
DD-region delimited by two disulfide bonds. Functional analysis of ComPsub defines a
new mode of DNA-binding involving the DD-region, adapted for exported DNA
receptors.