Conditions affecting production of functional muscle recombinant alpha-tropomyosin in Saccharomyces cerevisiae

Engineering strategies for enhanced heterologous protein production by Saccharomyces cerevisiae

Microbial proteins are promising substitutes for animal- and plant-based proteins. S. cerevisiae, a generally recognized as safe (GRAS) microorganism, has been frequently employed to generate heterologous proteins. However, constructing a universal yeast chassis for efficient protein production is still a challenge due to the varying properties of different proteins. With progress in synthetic biology, a multitude of molecular biology tools and metabolic engineering strategies have been employed to alleviate these issues. This review first analyses the advantages of protein production by S. cerevisiae. The most recent advances in improving heterologous protein yield are summarized and discussed in terms of protein hyperexpression systems, protein secretion engineering, glycosylation pathway engineering and systems metabolic engineering. Furthermore, the prospects for efficient and sustainable heterologous protein production by S. cerevisiae are also provided.

Mannose addition by yeast Pichia Pastoris on recombinant HER-2 protein inhibits recognition by the monoclonal antibody herceptin

We report here the generation of a full-length, highly glycosylated HER-2 oncoprotein using yeast strain, Pichia Pastoris. Upon treatment of secreted HER-2 with alpha-mannosidase, reactivity with the monoclonal antibody Herceptin is significantly increased. This phenomenon is due to glycosylation via mannose of the full-length HER-2 protein that extends over the antigenic epitope, which is recognized by Herceptin. The extensive glycosylation of HER-2 in Pichia Pastoris significantly increases its recognition and uptake by dendritic cells, which could be associated with increased vaccine performance.

Effects of cardiomyopathic mutations on the biochemical and biophysical properties of the human alpha-tropomyosin

Mutations in the protein alpha-tropomyosin (Tm) can cause a disease known as familial hypertrophic cardiomyopathy. In order to understand how such mutations lead to protein dysfunction, three point mutations were introduced into cDNA encoding the human skeletal tropomyosin, and the recombinant Tms were produced at high levels in the yeast Pichia pastoris. Two mutations (A63V and K70T) were located in the N-terminal region of Tm and one (E180G) was located close to the calcium-dependent troponin T binding domain. The functional and structural properties of the mutant Tms were compared to those of the wild type protein. None of the mutations altered the head-to-tail polymerization, although slightly higher actin binding was observed in the mutant Tm K70T, as demonstrated in a cosedimentation assay. The mutations also did not change the cooperativity of the thin filament activation by increasing the concentrations of Ca2+. However, in the absence of troponin, all mutant Tms were less effective than the wild type in regulating the actomyosin subfragment 1 Mg2+ ATPase activity. Circular dichroism spectroscopy revealed no differences in the secondary structure of the Tms. However, the thermally induced unfolding, as monitored by circular dichroism or differential scanning calorimetry, demonstrated that the mutants were less stable than the wild type. These results indicate that the main effect of the mutations is related to the overall stability of Tm as a whole, and that the mutations have only minor effects on the cooperative interactions among proteins that constitute the thin filament.

Expression of tropomyosin from Blattella germanica as a recombinant non-fusion protein in Pichia pastoris and comparison of its IgE reactivity with its native counterpart

Tropomyosins derived from invertebrates are well-known pan allergens. However, the allergenicities of recombinant tropomyosins are variable. Here, we undertook to compare the IgE-binding reactivities of native and recombinant German cockroach tropomyosins. Native tropomyosin was purified by ammonium sulfate fractionation, hydroxyapatite column chromatography, and electroelution, and recombinant tropomyosin was expressed in Pichia pastoris. The allergenicities of the native and recombinant tropomyosins were compared by ELISA inhibition analysis. Native German cockroach tropomyosin showed 18% IgE-binding reactivity to German cockroach sensitized sera. Recombinant tropomyosin was produced without fusion protein and its N-terminus was blocked like that of the native counterpart. The IgE-binding reactivity of the recombinant was found to be comparable to that of native tropomyosin over the concentration range 1-1000 ng/ml by ELISA inhibition testing. Recombinant German cockroach tropomyosin expressed in Pichia pastoris showed better allergenicity than that expressed in Escherichia coli. Other factors in addition to the structural differences of native and recombinant proteins may also influence the IgE reactivities of tropomyosins.