ADP-Ribosylargininyl reaction of cholix toxin is mediated through diffusible intermediates

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ADP-Ribosylargininyl reaction of cholix toxin is mediated through diffusible intermediates

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Title: ADP-Ribosylargininyl reaction of cholix toxin is mediated through diffusible intermediates
Author: Sung, Vicky M-H; Tsai, Chia-Lun

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Citation: Sung, Vicky M-H, and Chia-Lun Tsai. 2014. “ADP-Ribosylargininyl reaction of cholix toxin is mediated through diffusible intermediates.” BMC Biochemistry 15 (1): 26. doi:10.1186/s12858-014-0026-1. http://dx.doi.org/10.1186/s12858-014-0026-1.
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Abstract: Background: Cholix toxin is an ADP-ribosyltransferase found in non-O1/non-O139 strains of Vibrio cholera. The catalytic fragment of cholix toxin was characterized as a diphthamide dependent ADP-ribosyltransferase. Results: Our studies on the enzymatic activity of cholix toxin catalytic fragment show that the transfer of ADP-ribose to toxin takes place by a predominantly intramolecular mechanism and results in the preferential alkylation of arginine residues proximal to the NAD+ binding pocket. Multiple arginine residues, located near the catalytic site and at distal sites, can be the ADP-ribose acceptor in the auto-reaction. Kinetic studies of a model enzyme, M8, showed that a diffusible intermediate preferentially reacted with arginine residues in proximity to the NAD+ binding pocket. ADP-ribosylarginine activity of cholix toxin catalytic fragment could also modify exogenous substrates. Auto-ADP-ribosylation of cholix toxin appears to have negatively regulatory effect on ADP-ribosylation of exogenous substrate. However, at the presence of both endogenous and exogenous substrates, ADP-ribosylation of exogenous substrates occurred more efficiently than that of endogenous substrates. Conclusions: We discovered an ADP-ribosylargininyl activity of cholix toxin catalytic fragment from our studies in auto-ADP-ribosylation, which is mediated through diffusible intermediates. The lifetime of the hypothetical intermediate exceeds recorded and predicted lifetimes for the cognate oxocarbenium ion. Therefore, a diffusible strained form of NAD+ intermediate was proposed to react with arginine residues in a proximity dependent manner. Electronic supplementary material The online version of this article (doi:10.1186/s12858-014-0026-1) contains supplementary material, which is available to authorized users.
Published Version: doi:10.1186/s12858-014-0026-1
Other Sources: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4265445/pdf/
Terms of Use: This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAA
Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:13581200
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