6cp8

Publication Abstract from PubMed

Contact-dependent growth inhibition (CDI) is a form of interbacterial competition mediated by CdiB-CdiA two-partner secretion systems. CdiA effector proteins carry polymorphic C-terminal toxin domains (CdiA-CT), which are neutralized by specific CdiI immunity proteins to prevent self-inhibition. Here, we present the crystal structures of CdiA-CTCdiI complexes from Klebsiella pneumoniae 342 and Escherichia coli 3006. The toxins adopt related folds that resemble the ribonuclease domain of colicin D, and both are isoacceptor-specific tRNases that cleave the acceptor stem of deacylated tRNAGAU(Ile). Although the toxins are similar in structure and substrate specificity, CdiA-CT(Kp342) activity requires translation factors EF-Tu and EF-Ts, whereas CdiA-CT(EC3006) is intrinsically active. Furthermore, the corresponding immunity proteins are unrelated in sequence and structure. CdiI(Kp342) forms a dimeric beta sandwich, whereas CdiI(EC3006) is an alpha-solenoid monomer. Given that toxin-immunity genes co-evolve as linked pairs, these observations suggest that the similarities in toxin structure and activity reflect functional convergence.

Convergent Evolution of the Barnase/EndoU/Colicin/RelE (BECR) Fold in Antibacterial tRNase Toxins.,Gucinski GC, Michalska K, Garza-Sanchez F, Eschenfeldt WH, Stols L, Nguyen JY, Goulding CW, Joachimiak A, Hayes CS Structure. 2019 Sep 6. pii: S0969-2126(19)30281-3. doi:, 10.1016/j.str.2019.08.010. PMID:31515004^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.