High-level expression of human cytochrome P450 3A4 by co-expression with Human molecular chaperone HDJ-1 (Hsp40)

Bacterial expression, purification, and characterization of human cytochrome P450 3A4 without N-terminal modifications

In this communication we reported a bacterial system that over-expressed full-length wild-type (WT) human CYP3A4 in Escherichia coli (E. coli) at a level of 495 nmol/L culture. This level of expression was achieved by cloning the cDNA sequence of CYP3A4 WT to a pLW01-P450 vector and co-expressing it with chaperones GroEL/ES in bacterial C41(DE3) cells. Aided with a C-terminal His5-tag, the expressed CYP3A4 WT was purified to homogeneity with a specific content of 14.3 ± 2.0 nmole P450/mg protein using a single Ni-Penta agarose column. Like the N-terminal modified form (CYP3A4-NF14), CYP3A4 WT binds substrate testosterone with a typical sigmoidal feature at slightly higher affinity. Functional characterization revealed that CYP3A4 WT exhibited lower testosterone 6β-hydroxylase activities than CYP3A4-NF14 in reconstituted phospholipid systems. In addition, it was found that the 6β-hydroxylase activity of CYP3A4 WT was less dependent on excess cytochrome P450 oxidoreductase (POR), compared with CYP3A4-NF14. These results suggest that the N-terminal membrane anchor of CYP3A4 WT enhances its interactions with POR and marginally increases testosterone binding.

Folding of heterologous proteins in bacterial cell factories: Cellular mechanisms and engineering strategies

The expression of correctly folded and functional heterologous proteins is important in many biotechnological production processes, whether it is enzymes, biopharmaceuticals or biosynthetic pathways for production of sustainable chemicals. For industrial applications, bacterial platform organisms, such as E. coli, are still broadly used due to the availability of tools and proven suitability at industrial scale. However, expression of heterologous proteins in these organisms can result in protein aggregation and low amounts of functional protein. This review provides an overview of the cellular mechanisms that can influence protein folding and expression, such as co-translational folding and assembly, chaperone binding, as well as protein quality control, across different model organisms. The knowledge of these mechanisms is then linked to different experimental methods that have been applied in order to improve functional heterologous protein folding, such as codon optimization, fusion tagging, chaperone co-production, as well as strain and protein engineering strategies.

Transformation of Escherichia coli and protein expression using lipoplex mimicry

We investigated a "one-step" method for transformation of and protein expression in Escherichia coli (E. coli) using a complex of n-stearylamine, a cationic lipid, and plasmid DNA, which mimics lipoplex-based approaches. When E. coli cells were treated with the cationic lipid-plasmid complex, the transformation efficiencies were in the range of approximately 2-3 × 10(6) colony-forming units. Further increase in the efficiency was obtained by co-treatment with calcium chloride (or rubidium chloride) and the complexes. Moreover, after DNA transfer, E. coli cells successfully expressed plasmid-encoded proteins such as cytochrome P450s and glutathione-S-transferase without overnight incubation of the cells to form colonies, an indispensable step in other bacterial transformation methods. In this study, we provide a simple method for E. coli transformation, which does not require the preparation of competent cells. The present method also shortens the overall procedures for transformation and gene expression in E. coli by omitting the colony-forming step.

Human xanthine oxidase recombinant in E. coli: A whole cell catalyst for preparative drug metabolite synthesis

Human xanthine oxidoreductase (XOR), which is responsible for the final steps of the purine metabolism pathway and involved in oxidative drug metabolism, was successfully expressed in Escherichia coli BL21(DE3) Gold. Recombinant human (rh) XOR yielded higher productivity with the gene sequence optimized for expression in E.coli than with the native gene sequence. Induction of XOR expression with lactose or IPTG resulted in complete loss of activity whereas shake flasks cultures using media rather poor in nutrients resulted in functional XOR expression in the stationary phase. LB medium was used for a 25L fermentation in fed-batch mode, which led to a 5 fold increase of the enzyme productivity when compared to cultivation in shake flasks. Quinazoline was used as a substrate on the semi-preparative scale using an optimized whole cell biotransformation protocol, yielding 73mg of the isolated product, 4-quinazolinone, from 104mg of starting material.

Telomerase repeat amplification protocol (TRAP) activity upon recombinant expression and purification of human telomerase in a bacterial system

Telomerase biogenesis is a highly regulated process that solves the DNA end-replication problem. Recombinant expression has so far been accomplished only within a eukaryotic background. Towards structural and functional analyses, we developed bacterial expression of human telomerase. Positive activity by the telomerase repeat amplification protocol (TRAP) was identified in cell extracts of Escherichia coli expressing a sequence-optimized hTERT gene, the full-length hTR RNA with a self-splicing hepatitis delta virus ribozyme, and the human heat shock complex of Hsp90, Hsp70, p60/Hop, Hsp40, and p23. The Hsp90 inhibitor geldanamycin did not affect post-assembly TRAP activity. By various purification methods, TRAP activity was also obtained upon expression of only hTERT and hTR. hTERT was confirmed by tandem mass spectrometry in a ∼120 kDa SDS-PAGE fragment from a TRAP-positive purification fraction. TRAP activity was also supported by hTR constructs lacking the box H/ACA small nucleolar RNA domain. End-point TRAP indicated expression levels within 3-fold of that from HeLa carcinoma cells, which is several orders of magnitude below detection by the direct assay. These results represent the first report of TRAP activity from a bacterium and provide a facile system for the investigation of assembly factors and anti-cancer therapeutics independently of a eukaryotic setting.

Single vector system for efficient N-myristoylation of recombinant proteins in E. coli

BACKGROUND

N-myristoylation is a crucial covalent modification of numerous eukaryotic and viral proteins that is catalyzed by N-myristoyltransferase (NMT). Prokaryotes are lacking endogenous NMT activity. Recombinant production of N-myristoylated proteins in E. coli cells can be achieved by coexpression of heterologous NMT with the target protein. In the past, dual plasmid systems were used for this purpose.

METHODOLOGY/PRINCIPAL FINDINGS

Here we describe a single vector system for efficient coexpression of substrate and enzyme suitable for production of co- or posttranslationally modified proteins. The approach was validated using the HIV-1 Nef protein as an example. A simple and efficient protocol for production of highly pure and completely N-myristoylated Nef is presented. The yield is about 20 mg myristoylated Nef per liter growth medium.

CONCLUSIONS/SIGNIFICANCE

The single vector strategy allows diverse modifications of target proteins recombinantly coexpressed in E. coli with heterologous enzymes. The method is generally applicable and provides large amounts of quantitatively processed target protein that are sufficient for comprehensive biophysical and structural studies.

Heterologous expression and characterization of wild-type human cytochrome P450 1A2 without conventional N-terminal modification in Escherichia coli

In this study, wild-type human CYP1A2 without the conventional N-terminal modification (second codon GCT) or the truncation of the N-terminal hydrophobic region was functionally expressed in Escherichia coli. Its enzymatic properties were compared with N-terminally modified CYP1A2. Although modified CYP1A2 is almost all high-spin, some wild-type CYP1A2 shifted to low-spin. Spectral binding titrations with several ligands could be performed with wild-type enzyme, but not with modified enzyme. Kinetic parameters for several substrates were similar for the two CYP1A2 enzymes. However, the oxidation rates of phenacetin by modified enzyme were approximately 2-fold higher than those by wild-type enzyme. The intermolecular isotope effects were approximately 2 for phenacetin O-deethylation catalyzed by both enzymes. However, the wild-type enzyme, but not the modified enzyme, increased C-hydroxylation when O-deethylation rates were lowered by deuterium substitution. Molecular switching indicates that phenacetin rotates within the active site of wild-type enzyme and suggests a looser conformation in the active site of the wild-type enzyme than of the modified enzyme. These results reveal that the overall enzymatic properties of wild-type CYP1A2 enzyme are quite similar to those of modified CYP1A2, although its active site environment seems to differ from that of the modified enzyme.

Improvement in the expression of CYP2B6 by co-expression with molecular chaperones GroES/EL in Escherichia coli

Improvement of CYP2B6 expression was examined by co-expression with molecular chaperones GroES/EL. Although a CO-reduced difference spectrum was not detected in Escherichia coli transformed only by the CYP2B6-expressing vector, co-expression of GroES/EL resulted in high-level expression which reached over 2000 nmol P450/L. CYP2B6 was purified from the E. coli membrane with a high yield. Purified CYP2B6 showed 7-ethoxy-4-trifluoromethylcoumarin O-deethylase activity in a reconstitution system. This expression system would be useful for the production of large amounts of active CYP2B6 and for the detailed analysis of the enzyme.

Temperature effect on the functional expression of human cytochromes P450 2A6 and 2E1 inEscherichia coli

Human cytochromes P450 (CYP) 2A6 and 2E1 are of great interest because of their important roles in the oxidation of numerous drugs and carcinogens. Bacterial expression systems, especially Escherichia coli cells, have been widely used for the production of various CYP enzymes in order to obtain high yield of proteins. The expression methods usually employ longer culture time (30-72 h) at lower temperature (usually under 30 degrees C). Expression levels of CYPs 2A6 and 2E1 at 37 degrees C were compared to those at 280 degrees C, which is a usual temperature used in most bacterial expression systems for human CYP expression. Within 18 h the expression levels of CYPs 2A6 and 2E1 reached up to 360 and 560 nmol per liter culture at 37 degrees C, respectively, which are compatible with those of 36 h culture at 280 degrees C. The activities of CYPs expressed at 37 degrees C were also comparable to those expressed at 28 degrees C. The present over-expression system can be useful for rapid production of large amounts of active human CYPs 2A6 and 2E1 in E. coli.