Activation of an anti-bacterial toxin by the biosynthetic enzyme CysK: mechanism of binding, interaction specificity and competition with cysteine synthase

0478453 - ÚOCHB 2018 RIV GB eng J - Článek v odborném periodiku
Benoni, Roberto - Beck, C. M. - Garza-Sánchez, F. - Bettati, S. - Mozzarelli, A. - Hayes, C. S. - Campanini, B.
Activation of an anti-bacterial toxin by the biosynthetic enzyme CysK: mechanism of binding, interaction specificity and competition with cysteine synthase.
Scientific Reports. Roč. 7, Aug 18 (2017), č. článku 8817. ISSN 2045-2322. E-ISSN 2045-2322
Institucionální podpora: RVO:61388963
Klíčová slova: O-acetylserine sulfhydrylase * dependent growth inhibition * Salmonella typhimurium LT-2
Obor OECD: Biochemistry and molecular biology
Impakt faktor: 4.122, rok: 2017
https://www.nature.com/articles/s41598-017-09022-6

Contact-dependent growth inhibition (CDI) is a wide-spread mechanism of inter-bacterial competition. CDI+ bacteria deliver CdiA-CT toxins into neighboring bacteria and produce specific immunity proteins that protect against self-intoxication. The CdiA-CT toxin from uropathogenic Escherichia coli 536 is a latent tRNase that is only active when bound to the cysteine biosynthetic enzyme CysK. Remarkably, the CysK: CdiA-CT binding interaction mimics the 'cysteine synthase' complex of CysK: CysE. The C-terminal tails of CysE and CdiA-CT each insert into the CysK active-site cleft to anchor the respective complexes. The dissociation constant for CysK: CdiA-CT (K-d similar to 11 nM) is comparable to that of the E. coli cysteine synthase complex (K-d similar to 6 nM), and both complexes bind through a two-step mechanism with a slow isomerization phase after the initial encounter. However, the second-order rate constant for CysK: CdiA-CT binding is two orders of magnitude slower than that of the cysteine synthase complex, suggesting that CysE should outcompete the toxin for CysK occupancy. However, we find that CdiA-CT can effectively displace CysE from pre-formed cysteine synthase complexes, enabling toxin activation even in the presence of excess competing CysE. This adventitious binding, coupled with the very slow rate of CysK: CdiA-CT dissociation, ensures robust nuclease activity in target bacteria.
Trvalý link: http://hdl.handle.net/11104/0274571