A novel N-terminal region of the membrane β-hexosyltransferase: its role in secretion of soluble protein by Pichia pastoris
Dagher, Suzanne F. and Bruno-Bárcena, José M.,, 162, 23-34 (2016),
doi = https://doi.org/10.1099/mic.0.000211,
publicationName = Microbiology Society,
issn = 1350-0872,
abstract= The β-hexosyltransferase (BHT) from Sporobolomyces singularis is a membrane-bound enzyme that catalyses transgalactosylation reactions to synthesize galacto-oligosaccharides (GOSs). To increase the secretion of the active soluble version of this protein, we examined the uncharacterized novel N-terminal region (amino acids 1–110), which included two predicted endogenous structural domains. The first domain (amino acids 1–22) may act as a classical leader while a non-classical signal was located within the remaining region (amino acids 23–110). A functional analysis of these domains was performed by evaluating the amounts of the rBHT forms secreted by recombinant P. pastoris strains carrying combinations of the predicted structural domains and the α mating factor (MFα) from Saccharomyces cerevisiae as positive control. Upon replacement of the leader domain (amino acids 1–22) by MFα (MFα-rBht (23-594)), protein secretion increased and activity of both soluble and membrane-bound enzymes was improved 53- and 14-fold, respectively. Leader interference was demonstrated when MFα preceded the putative classical rBHT(1-22) leader (amino acids 1–22), explaining the limited secretion of soluble protein by P. pastoris (GS115 : : MFα-rBht (1-594)). To validate the role of the N-terminal domains in promoting protein secretion, we tested the domains using a non-secreted protein, the anti-β-galactosidase single-chain variable antibody fragment scFv13R4. The recombinants carrying chimeras of the N-terminal 1–110 regions of rBHT preceding scFv13R4 correlated with the secretion strength of soluble protein observed with the rBHT recombinants. Finally, soluble bioactive HIS-tagged and non-tagged rBHT (purified to homogeneity) obtained from the most efficient recombinants (GS115 : : MFα-rBht (23-594)-HIS and GS115 : : MFα-rBht (23-594)) showed comparable activity rates of GOS generation.,
language=,
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