The structure of a contact-dependent growth-inhibition (CDI) immunity protein from Neisseria meningitidis MC58

Contact-dependent growth inhibition (CDI) is an important mechanism of intercellular competition between neighboring Gram-negative bacteria. CDI systems encode large surface-exposed CdiA effector proteins that carry a variety of C-terminal toxin domains (CdiA-CTs). All CDI+ bacteria also produce CdiI immunity proteins that specifically bind to the cognate CdiA-CT and neutralize its toxin activity to prevent auto-inhibition. Here, the X-ray crystal structure of a CdiI immunity protein from Neisseria meningitidis MC58 is presented at 1.45 Å resolution. The CdiI protein has structural homology to the Whirly family of RNA-binding proteins, but appears to lack the characteristic nucleic acid-binding motif of this family. Sequence homology suggests that the cognate CdiA-CT is related to the eukaryotic EndoU family of RNA-processing enzymes. A homology model is presented of the CdiA-CT based on the structure of the XendoU nuclease from Xenopus laevis. Molecular-docking simulations predict that the CdiA-CT toxin active site is occluded upon binding to the CdiI immunity protein. Together, these observations suggest that the immunity protein neutralizes toxin activity by preventing access to RNA substrates.

Source: Acta Crystallographica Section F - May 20, 2015 Category: Biochemistry Authors: Tan, K.Johnson, P.M.Stols, L.Boubion, B.Eschenfeldt, W.Babnigg, G.Hayes, C.S.Joachimiak, A.Goulding, C.W. Tags: contact-dependent growth inhibition CdiA-CT toxin domain CdiI immunity protein – immunity protein complex Neisseria meningitidis docking studies research communications Source Type: research