Parallel N- and C-Terminal Truncations Facilitate Purification and Analysis of a 155-kDa Cold-Adapted Type-I Pullulanase

Effects of Lower Temperature on Expression and Biochemical Characteristics of HCV NS3 Antigen Recombinant Protein

The nonstructural antigen protein 3 of the hepatitis C virus (HCV NS3), commonly-used for HCV ELISA diagnosis, possesses protease and helicase activities. To prevent auto-degradation, a truncated NS3 protein was designed by removing the protease domain. Firstly, it was overexpressed in E. coli by IPTG induction under two different temperatures (25 and 37 °C), and purified using affinity chromatography to attain homogeneity above 90%. The molecular mass of purified protein was determined to be approx. 55 kDa. While lowering the temperature from 37 to 25 °C, the yield of the soluble fraction of HCV NS3 was increased from 4.15 to 11.1 mgL−1 culture, which also improved the antigenic activity and specificity. The protein stability was investigated after long-term storage (for 6 months at −20 °C) revealed no loss of activity, specificity, or antigenic efficacy. A thermal stability study on both freshly produced and stored HCV NS3 fractions at both temperatures showed that the unfolding curve profile properly obey the three-state unfolding mechanism. In the first transition phase, the midpoints of the thermal denaturation of fresh NS3 produced at 37 °C and 25 °C, and that produced after long-term storage at 37 °C and 25 °C, were 59.7 °C, 59.1 °C, 55.5 °C, and 57.8 °C, respectively. Microplates coated with the fresh NS3 produced at 25 °C or at 37 °C that were used for the HCV ELISA test and the diagnosis outcome were compared with two commercial kits—Abbott HCV EIA 2.0 and Ortho HCV EIA 3.0. Results indicated that the specificity of the HCV NS3 produced fresh at 25 °C was higher than that of the fresh one at 37 °C, hence showing potential for application in HCV ELISA diagnosis.

Phenotypic suppression caused by resonance with light-dark cycles indicates the presence of a 24-hours oscillator in yeast and suggests a new role of intrinsically disordered protein regions as internal mediators

The mutual interaction between environment and life is a main topic of biological sciences. An interesting aspect of this interaction is the existence of biological rhythms spanning all the levels of organisms from bacteria to humans. On the other hand, the existence of a coupling between external oscillatory stimuli and adaptation and evolution rate of biological systems is a still unexplored issue. Here we give the demonstration of a substantial increase of heritable phenotypic changes in yeast, an organism lacking a photoreception system, when growing at 12 h light/dark cycles, with respect to both stable dark (or light) or non-12 + 12 h cycling. The model system was a yeast strain lacking a gene whose product is at the crossroad of many different physiological regulations, so ruling out any simple explanation in terms of increase in reverse gene mutations. The abundance of intrinsically disordered protein regions (IDPRs) in both deleted gene product and in its vast ensemble of interactors supports the hypothesis that resonance with the environmental cycle might be mediated by intrinsic disorder-driven interactions of protein molecules. This result opens to the speculation of the effect of environment/biological resonance phenomena in evolution and of the role of protein intrinsically disordered regions as internal mediators.Communicated by Ramaswamy H. Sarma.