title: Strain engineering to prevent norleucine incorporation during recombinant protein production in Escherichia coli.
abstract: Incorporation of norleucine in place of methionine residues during recombinant protein production in Escherichia coli is well known. Continuous feeding of methionine is commonly used in E. coli recombinant protein production processes to prevent norleucine incorporation. Although this strategy is effective in preventing norleucine incorporation, there are several disadvantages associated with continuous feeding. Continuous feeding increases the operational complexity and the overall cost of the fermentation process. In addition, the continuous feed leads to undesirable dilution of the fermentation medium possibly resulting in lower cell densities and recombinant protein yields. In this work, the genomes of three E. coli hosts were engineered by introducing chromosomal mutations that result in methionine overproduction in the cell. The recombinant protein purified from the fermentations using the methionine overproducing hosts had no norleucine incorporation. Furthermore, these studies demonstrated that the fermentations using one of the methionine overproducing hosts exhibited comparable fermentation performance as the control host in three different recombinant protein production processes.
authors.affiliation: Dept. of Late Stage Cell Culture, Genentech Inc., South San Francisco, CA, 94080.
authors.forename: Karthik
authors.initials: K
authors.lastname: Veeravalli
authors.forename: Michael W
authors.initials: MW
authors.lastname: Laird
authors.forename: Mark
authors.initials: M
authors.lastname: Fedesco
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: X Christopher
authors.initials: XC
authors.lastname: Yu
mesh_terms: D000595:Amino Acid Sequence; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005110:Extracellular Space / Q000737:chemistry; D005285:Fermentation; D060847:Metabolic Engineering / Q000379:methods*; D008715:Methionine / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D009646:Norleucine / Q000737:chemistry / Q000378:metabolism*; D010710:Phosphates / Q000032:analysis; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D010710:Phosphates; D011994:Recombinant Proteins; D009646:Norleucine; D008715:Methionine
keywords: fermentation; incorporation; methionine; norleucine; recombinant protein; sequence variant