Pressure and Temperature Effects on Protein Solutions

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Excess partial molar enthalpy of lysozyme in aqueous alcohol was measured using isothermal titration calorimetry. It was suggested that occupancy by the alcohol of a binding site on the surface of the protein may not be necessary for the alcohol to affect the properties of the protein. Pressure dependences of the solubiity for lysozyme and glycine in water measured. The formaer increased and the latter decreased with increasing pressure though both solubilities increased with increasing temperature. It suggests that the pressrue is one of key parameter to consider the protein hydration in the stand point of the constituent amino acids.High-pressure FT-IR of Myoglobin (Mb) was measured in the range -10-70ﾟC.Pressure dependence of the second structure of Mb follows two state model. The structure irreversibly changes to random coil forming intermolecular beta-sheet with increasing temperature though it becomes reversible at low temperature.It was, succeeded in expressing yeast cytochrome c in E.coli through construction of a plasmid for the co-expression of cytochrome c heme lyase and cytochrome c. The yield of wild-type cytochrome c from this system is relatively high. Variants in which the crucial Met80 ligand to the heme iron is replaced with Ala and that do no support respiration can be expressed in E.coli demonstrated that Lys72 is not trimethyllated postsynthetically as it is when expressed in yeast. This finding is no surprising because presumably E.coli does not posses the transmethylase enzyme that catalyzes this modification reaction.