Urea titration of a lipase from Pseudomonas sp. reveals four different conformational states, with a stable partially folded state explaining its high aggregation propensity

Abstract The conversion of soluble proteins into amyloid fibrils has importance in protein chemistry, biology, biotechnology and medicine. A novel lipase from Pseudomonas sp. was previously shown to have an extremely high aggregation propensity. It therefore herein studied elucidate the physicochemical structural determinants this extreme behaviour. Amyloid-like structures were found form samples up 2.5–3.0 M using Thioflavin T fluorescence Congo red binding assays. However, dynamic light scattering (DLS), static turbidimetry revealed existence aggregates 4.0 M urea, without amyloid-like structure. Two monomeric conformational states detected with intrinsic fluorescence, 8-anilinonaphthalene-1-sulfonate (ANS) circular dichroism. These further characterized 7.5 M 4.5 M urea enzymatic activity measurements, tryptophan quenching, DLS nuclear magnetic resonance (NMR) consist a largely disordered partially folded state, respectively, latter appearing stable, cooperative, fairly compact, non-active, α-helical, buried hydrophobic residues. persistence stable structure concentrations absence sequence characteristics typical propensity, explains tendency enzyme structures.