Protein palindromes discovered in bacterial antitoxins

C. crescentus VapBC apo-DNA morph

Crystal structure of the C. crescentus VapBC complex bound to DNA with disordered tails modelled.

Today, we have published a paper in Nucleic Acids Research describing crystal structures of the Caulobacter crescentus VapBC toxin-antitoxin complex both in the apo form and bound to operator DNA.

For the first time, we have detailed structures of the same TA complex both in the apo form and bound to DNA. Unexpectedly, the “tails” on the antitoxin molecules bind two toxin molecules each. We show that this is possible due to a “protein palindrome” sequence located near the C termini of the antitoxins. Even more surprising, the tails swap position upon binding DNA, suggesting that they might serve to interlock the complex when bound to the operator region. Sequence analysis of more than 4,000 VapB sequences finally reveal that this phenomenon is widespread among bacterial antitoxins.

For more information, have a look at the paper in Nucleic Acids Research.

Bendtsen, K. L., Xu, K., Luckmann, M., Winther, K. S., Shah, S. A., Pedersen, C. N. S., and Brodersen, D. E. (2017) “Toxin inhibition in C. crescentus VapBC1 is mediated by a flexible pseudo- palindromic protein motif and modulated by DNA binding”, Nucleic Acids Res, 45(5):2875-2886.