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Processing and functional display of the 86 kDa heterodimeric penicillin G acylase on the surface of phage fd.

ABSTRACT: The large heterodimeric penicillin G acylase from Alcaligenes faecalis was displayed on the surface of phage fd. We fused the coding sequence (alpha subunit-internal peptide-beta subunit) to the gene of a phage coat protein. A modified g3p signal sequence was used to direct the polypeptide to the periplasm. Here we show that a heterodimeric enzyme can be expressed as a fusion protein that matures to an active biocatalyst connected to the coat protein of phage fd, resulting in a phage to which the beta-subunit is covalently linked and the alpha-subunit is non-covalently attached. The enzyme can be displayed either fused to the minor coat protein g3p or fused to the major coat protein g8p. In both cases the penicillin G acylase on the phage has the same Michaelis constant as its freely soluble counterpart, indicating a proper folding and catalytic activity of the displayed enzyme. The display of the heterodimer on phage not only allows its further use in protein engineering but also offers the possibility of applying this technology for the excretion of the enzyme into the extracellular medium, facilitating purification of the protein. With the example of penicillin acylase the upper limit for a protein to become functionally displayed by phage fd has been further explored. Polyvalent display was not observed despite the use of genetic constructs designed for this aim. These results are discussed in relation to the pore size being formed by the g4p multimer.

SUBMITTER: Verhaert RM

PROVIDER: S-EPMC1220479 | biostudies-other | 1999 Sep

REPOSITORIES: biostudies-other

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Project description:To take full advantage of recombinant Pichia pastoris (Komagataella phaffii) as a production system for heterologous proteins, the complex protein secretory process should be understood and optimised by circumventing bottlenecks. Typically, little or no attention has been paid to the fate of newly synthesised protein inside the cell, or its passage through the secretory pathway, and only the secreted product is measured. However, the system's productivity (i.e. specific production rate qp), includes productivity of secreted (qp,extra) plus intracellularly accumulated (qp,intra) protein. In bioreactor cultivations with P. pastoris producing penicillin G acylase, we studied the dynamics of product formation, i.e. both the specific product secretion (qp,extra) and product retention (qp,intra) as functions of time, as well as the kinetics, i.e. productivity in relation to specific growth rate (?). Within the time course, we distinguished (I) an initial phase with constant productivities, where the majority of product accumulated inside the cells, and qp,extra, which depended on ? in a bell-shaped manner; (II) a transition phase, in which intracellular product accumulation reached a maximum and productivities (intracellular, extracellular, overall) were changing; (III) a new phase with constant productivities, where secretion prevailed over intracellular accumulation, qp,extra was linearly related to ? and was up to three times higher than in initial phase (I), while qp,intra decreased 4-6-fold. We show that stress caused by heterologous protein production induces cellular imbalance leading to a secretory bottleneck that ultimately reaches equilibrium. This understanding may help to develop cultivation strategies for improving protein secretion from P. pastoris.Key Points• A novel concept for industrial bioprocess development.• A Relationship between biomass growth and product formation in P. pastoris.• A Three (3) phases of protein production/secretion controlled by the AOX1-promoter.• A Proof of concept in production of industrially relevant penicillin G acylase.

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Processing and functional display of the 86 kDa heterodimeric penicillin G acylase on the surface of phage fd.

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