title: Heterologous expression, purification, and characterization of cytochrome P450sca-2 and mutants with improved solubility in Escherichia coli.
abstract: Pravastatin, an important cholesterol lowering drug, is currently produced by hydroxylation of mevastatin (ML-236B) with Streptomyces carbophilus, in which the enzyme P450sca-2 plays a key role. Little information on the recombinant expression of this enzyme is available. As it is of industrial interest to develop an alternative simplified enzymatic process for pravastatin, as a first step, further study on the heterologous expression of this enzyme is warranted. We report here, for the first time, the purification, and characterization of P450sca-2 expressed in Escherichia coli. A synthetic gene encoding P450sca-2 was designed to suit the standard codon usage of E. coli. Expression of P450sca-2 in E. coli under optimized conditions yielded about 100 nmol purified active P450sca-2 per liter. Directed evolution was further carried out to improve the soluble expression level. In the absence of a facile and sensitive assay, green fluorescent protein (GFP) was used as a reporter to enable high-throughput screening. After three rounds of evolution by error-prone PCR and DNA shuffling, six almost totally soluble mutants were obtained, with the soluble expression levels dramatically improved by about 30-fold. For six most frequently occurring mutations, the corresponding single mutants were created to dissect the effects of these mutations. A single mutation, P159A, was found to be responsible for most of the enhanced solubility observed in the six mutants, and the corresponding single mutant also retained the hydroxylation activity. Our study provides a foundation for future work on improving functional expression of P450sca-2 in E. coli.
authors.affiliation: Department of Chemical Engineering, Tsinghua University, 1 Tsinghua Garden Road, Beijing 100084, China.
authors.forename: Pan
authors.initials: P
authors.lastname: Li
authors.forename: Hong
authors.initials: H
authors.lastname: Guan
authors.forename: Jin
authors.initials: J
authors.lastname: Li
authors.forename: Zhanglin
authors.initials: Z
authors.lastname: Lin
mesh_terms: D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000737:chemistry; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D009154:Mutation; D016133:Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D012995:Solubility; D013302:Streptomyces / Q000201:enzymology
chemical_list: D050505:Mutant Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D003577:Cytochrome P-450 Enzyme System