Mechanistic insights into osmolyte action in protein stabilization under harsh conditions: N-methylacetamide in glycine betaine-urea mixture

- Glycine betaine (GB) increases and urea decreases the solvation of N-methylacetamide.
- GB significantly reduces hydrophobic interactions between N-methylacetamide and urea.
- The presence of GB excludes urea from N-methylacetamide surface.
- Direct interactions between GB and urea are important in counteracting the urea effect.

Glycine betaine (GB), a small naturally occurring osmolyte, stabilizes proteins and counteracts harsh denaturing conditions such as extremes of temperature, cellular dehydration, and presence of high concentration of urea. In spite of several studies on understanding mechanism of protein stabilization and counteraction of these harsh conditions by osmolytes, studies centred on GB, one of the most important osmolyte, are scarce, hence, there is need for more investigations. To explore mechanism of protein stabilization and counteraction of denaturing property of urea by GB, molecular dynamics studies of N-methylacetamide (NMA), a model peptide representing denatured state of a protein, in the presence of GB, urea, and GB-urea mixture were carried out. The results show that GB and urea work such that the strength of GB as a protecting osmolyte is increased and the denaturing ability of urea is decreased in the GB-urea mixture. It can be inferred that GB counteracts urea by decreasing its hydrophobic interactions with proteins. The mutual interactions between GB and urea also play an important role in protein stabilization. This study provides insights on osmolyte induced counteraction of denaturing property of urea.