Stabilizing osmolytes' effects on the structure, stability and function of tc-tenecteplase: A one peptide bond...

Organic osmolytes, as major cellular compounds, cause protein stabilization in the native form. In the present study, the possible chaperone effects of the three naturally occurring osmolytes on the two-chain form of tenecteplase (tc-TNK), a recombinant, genetically engineered mutant tissue plasminogen activator, have been explored by using circular dichroism, steady-state fluorescence, UV-Visible spectroscopy, and in silico experiments. The tc-TNK is derived from the one-chain protein upon disruption of one peptide bond. Thermal denaturation experiments showed a slightly more stabilizing effect of the three co-solvents on the single-chain TNK (sc-TNK) in comparison to that on tc-TNK. Unlike single-chain tenecteplase, the two-chain form undergoes reversible denaturation which is somehow perturbed in some cases as the result of the presence of osmolytes. Very minor changes in the secondary structure and the tertiary structure were observed. The molecular dynamics simulations and comparative structural analysis of catalytic domain of the protein in the single-chain and two-chain forms in pure water, mannitol/water, trehalose/water, and sucrose/water showed that while the stabilizing effect of the three osmolytes on tc-TNK might be induced by preferential accumulation of these molecules around the nonpolar and aromatic residues, that is to say, fewer water-hydrophobic residues' interactions in tc-TNK, sc-TNK is stabilized by preferential exclusion effect.