Design of stable circular permutants of the GroEL chaperone apical domain.

Enhancing protein stability holds paramount significance in biotechnology, therapeutics, and the food industry. Circular permutations offer a distinctive avenue for manipulating protein stability while keeping intra-protein interactions intact. Amidst the creation of circular permutants, determining the optimal placement of the new N- and C-termini stands as a pivotal, albeit largely unexplored, endeavor. In this study, we employed PONDR-FIT's predictions of disorder propensity to guide the design of circular permutants for the GroEL apical domain (residues 191-345). Our underlying hypothesis posited that a higher predicted disorder value would correspond to reduced stability in the circular permutants, owing to the increased likelihood of fluctuations in the novel N- and C-termini. To substantiate this hypothesis, we engineered six circular permutants, positioning glycines within the loops as locations for the new N- and C-termini. We demonstrated the validity of our hypothesis along the set of the designed circular permutants, as supported by measurements of melting temperatures by circular dichroism and differential scanning microcalorimetry. Consequently, we propose a novel computational methodology that rationalizes the design of circular permutants with projected stability. Video Abstract.

The influence of Pseudomonas syringae on water freezing and ice melting.

Pseudomonas syringae is a widely spread plant pathogen known to have ice-nucleating proteins that serve as crystallization sites promoting ice growth at near-zero temperatures. Three temperatures that characterize water freezing and ice melting are (i) the freezing point of water, (ii) the temperature of coexistence of ice and water, and (iii) the melting point of ice. Here we show the influence of different concentrations of P. syringae on these three parameters. P. syringae appears to affect both the freezing point of water and the temperature of the coexistence of ice and water. Additionally, we propose a research technique for studying the freezing/melting process that is simple and requires no complex equipment.