Glycine betaine (GB) or N,N,N-trimethyl glycine is a naturally occurring osmo-protectant, responsible for maintaining osmosis of environmentally stressed cells by retaining intracellular water and cytoplasmic volume. Additionally, it has also been shown that GB can  act as a thermo-protectant, stabilizing the native structure of proteins as well as polynucleotides and counteracts the denaturing effect of destabilizing osmolytes like urea. Following the widely accepted mechanism of action for these protein-protecting osmolytes, it is believed that GB acts by being preferentially excluded from the surface of proteins. This ‘non-direct interaction’ mechanism would exclude the possibility that GB can destabilize proteins, which requires direct interactions between the osmolyte molecules and protein backbone units and/or sidechains. However, as a molecular cation, it is expected that GB can engage in cation-π interactions with aromatic sidechains opening the possibility for GB to directly interact with aromatic amino acids in a protein.  This enables the osmolyte to destabilize proteins that are rich in aromatic residues but do not have a specific binding site tailored for quaternary amines. In this study we hypothesize that GB can act as a denaturant toward proteins that are stabilized by aromatic residues, especially tryptophan, and its denaturing efficiency is higher than that of less methylated analogues of osmolytes. To validate this hypothesis, we studied the effect of GB on (1) the hydration status of an indole analog (the fluorophore of tryptophan), 7-cyanoindole, and (2) the thermal stability of a mutant of the Trpzip2 and Trpzip5 β-hairpins wherein the native tryptophan amino acids are replaced by  5-cyanotryptophan. Our steady state and time resolved fluorescence and circular dichroism measurements show that for such a peptides rich in aromatic residues, GB indeed acts as a denaturant rather than an osmo-protectant through cation-π interactions.<br/>

Can osmo-protectant glycine-betaine denature proteins?

Macromolecular Chemistry: The Second Century

[Author Benefits](https://scimeetings.acs.org/?utm_source=pubs_content_marketing&utm_medium=website&utm_campaign=0320_MCF_NPI_Launch_Spring_Homepage&ref=pubs_content_marketing)

[How to use SciMeetings](https://storage.googleapis.com/dl.morressier.com/acs/SciMeetings-ACSSpring2020-HowToGuide_M3020-Final.pdf)

[Frequently Asked Questions](https://storage.googleapis.com/dl.morressier.com/acs/SciMtng_ACSNMSp2020_FAQ_M3120_Final.pdf)

ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.