Amanda Emmanuelle Sales

Effects of osmolytes on protein-solvent interactions in crowded environment: Analyzing the effect of TMAO on proteins in crowded solutions.

We analyzed the effect of a natural osmolyte, trimethylamine N-oxide (TMAO), on structural properties and conformational stabilities of several proteins under macromolecular crowding conditions by a set of biophysical techniques. We also used the solvent interaction analysis method to look at the peculiarities of the TMAO-protein interactions under crowded conditions. To this end, we analyzed the partitioning of these proteins in TMAO-free and TMAO-containing aqueous two-phase systems (ATPSs). These ATPSs had the same polymer composition of 6.0 wt.% PEG-8000 and 12.0 wt.% dextran-75, and same ionic composition of 0.01 M K/NaPB, pH 7.4. These analyses revealed that there is no direct interaction of TMAO with proteins, suggesting that the TMAO effects on the protein structure in crowded solutions occur via the effects of this osmolyte on solvent properties of aqueous media. The effects of TMAO on protein structure in the presence of polymers were rather complex and protein-specific. Curiously, our study revealed that in highly concentrated polymer solutions, TMAO does not always act to promote further protein folding.

Purification of a fibrinolytic protease from Mucor subtilissimus UCP 1262 by aqueous two-phase systems (PEG/sulfate)

A fibrinolytic protease from M. subtilissimus UCP 1262 was recovered and partially purified by polyethylene glycol (PEG)/sodium sulfate aqueous two-phase systems (ATPS). The simultaneous influence of PEG molar mass, PEG concentration and sulfate concentration on the enzyme recovery was first investigated using a 2(3) full factorial design, and the Response Surface Methodology used to identify the optimum conditions for enzyme extraction by ATPS. Once the best PEG molar mass for the process had been selected (6000g/mol), a two-factor central composite rotary design was applied to better evaluate the effects of the other two independent variables. The fibrinolytic enzyme was shown to preferentially partition to the bottom phase with a partition coefficient (K) ranging from 0.2 to 0.7. The best results in terms of enzyme purification were obtained with the system formed by 30.0% (w/w) PEG 6000g/mol and 13.2% (w/w) sodium sulfate, which ensured a purification factor of 10.0, K of 0.2 and activity yield of 102.0%. SDS-PAGE and fibrin zymography showed that the purified protease has a molecular mass of 97kDa and an apparent isoelectric point of 5.4. When submitted to assays with different substrates and inhibitors, it showed selectivity for succinyl-l-ala-ala-pro-l-phenylalanine-p-nitroanilide and was almost completely inhibited by phenylmethylsulfonyl fluoride, behaving as a chymotrypsin-like protease. At the optimum temperature of 37°C, the enzyme residual activity was 94 and 68% of the initial one after 120 and 150min of incubation, respectively. This study demonstrated that M. subtilissimus protease has potent fibrinolytic activity compared with similar enzymes produced by solid-state fermentation, therefore it may be used as an agent for the prevention and therapy of thrombosis. Furthermore, it appears to have the advantages of low cost production and simple purification.

Hydrophobicity-dependent effects of polymers on different protein conformations

We have previously shown that increasing the hydrophobicity of PEG by adding a methyl group to every other monomer unit allowed the resulting polymer to alter protein folding and inhibit protein aggregation to amyloid fibrils. As a continuation of this work, we analyzed here the effects of this substitution on the structural properties of proteins capable of adopting multiple conformations (folded, and different partially folded states, e.g. a molten globule-like intermediate) at mild denaturing conditions. To this end, we have selected several proteins (α-lactalbumin, apomyoglobin, carbonic anhydrase, staphylococcal nuclease, and cytochrome c) and examined them at different conditions where they exist in different partially folded conformations (pH, temperature, salt concentrations, presence of cofactors). We were especially interested in the relative sensitivity of partially folded (e.g. molten globule) conformations of these proteins to the presence of polymers as these conformations are often the most sensitive to the environment. We used far-UV CD to test the changes in the protein secondary structure, near-UV CD to monitor changes in the tertiary structure, and quenching of intrinsic protein fluorescence by acrylamide to evaluate changes in the solvent accessibility of aromatic residues. We found that the complexity of the effect of polymers on protein structure cannot be ascribed solely to macromolecular crowding since the behavior of proteins in solutions containing polymers is dependent on protein and polymer structure. We also cannot exclude the possibility that the structures of both proteins and polymers determine the balance between attractive and repulsive forces that drive protein–polymer interactions.

Optimization of production, biochemical characterization and in vitro evaluation of the therapeutic potential of fibrinolytic enzymes from a new Bacillus amyloliquefaciens

The capacity of fibrinolytic enzymes to degrade blood clots makes them of high relevance in medicine and in the pharmaceutical industry. In this work, forty-three microorganisms of the genus Bacillus were evaluated for their potential to produce fibrinolytic proteases. Thirty bacteria were confirmed as producers of fibrinolytic enzymes, the best results obtained for the strain Bacillus amyloliquefaciens UFPEDA 485. The optimization of the enzyme production conditions was done by a central composite design (CCD) star 23 that allowed to define the optimal conditions for soybean flour and glucose concentrations and agitation rate. The highest fibrinolytic activity (FA) of 813 U mL–1 and a degradation of blood clot in vitro of 62% were obtained in a medium with 2% (w/v) of soybean flour and 1% (w/v) glucose at 200 rpm after 48 h of cultivation, at pH 7.2 and 37 °C. The obtained fibrinolytic enzyme was characterized biochemically. Fibrinolytic activity was inhibited by PMSF (fluoride methylphenylsulfonyl - C7H7FO2S) 91.52% and EDTA (ethylenediaminetetraacetic acid - C10H16N2O8) 89.4%, confirming to be a serine-metallo protease. The optimum pH and temperature were 7.0 and 37 oC, respectively, and the enzyme was stable for 12 h. The fibrinolytic activity at physiological conditions of this enzyme produced by Bacillus amyloliquefaciens UFPEDA 485, as well as its long term stability, demonstrate that it has suitable characteristics for human and veterinary applications, and promises to be a powerful drug for the treatment of vascular diseases.