Effects of Oxygen on Recombinant Protein Expression

Abstract

Efforts to increase cell growth and protein yields need to be complemented by the maintenance of the quality of the protein produced. Elevated oxygen pressure or rapid increases in oxygen content can cause oxidative stress within the cells, leading to oxidation of specific proteins and nucleotide sequences. In addition, transient or steady-state anoxic conditions can cause limitations in amino acid production and plasmid stability. Major pathways and mechanisms of oxidative damage to proteins expressed in bacteria are reviewed. Damage to nucleic acids involved in gene expression also is considered. The methodologies for identifying oxidative damage to macromolecules are improving but are not yet adequate for on-line feedback. This limits our ability to integrate information about these phenomena and the cellular responses into a quantitative model. Enough information is available, however, to consider changes in the time profile of dissolved oxygen as a cause for poor process performance.

A New Type 2 Copper Cysteinate Azurin

“…Modeling-Modeling was started by taking the crystal structure of wild type azurin and replacing His 117 for a glycine and Asn 42 for a cysteine using Swiss-Pdb Viewer version 3.51.…”

“…We demonstrate in this work that the protein framework of the doubly mutated protein can undergo a major rearrangement leading to a metal site in which Cys 42 acts as one of the copper ligands. This site has a unique spectroscopic fingerprint.…”

“…This site has a unique spectroscopic fingerprint. Moreover, when the copper site is reconstituted by incubating the apoprotein with Cu(II), the Cys 42 functions as an arm that catches the metal ion and carries it over to the active site where it becomes coordinated by, among others, a second cysteine, Cys 112 . This process may be relevant for a better understanding of the in vivo process of copper uptake and transfer by copper chaperones.…”

High Yield Production of Heterologous Proteins with Escherichia coli

“…In recent times, the secondary role of oxygen on maintenance of cell physiology and quality of the recombinant protein have been a major concern for the high volumetric yield of recombinant protein from E. coli 54,71 . Fluctuations in oxygen content during high productive fermentation process can cause oxidative stress within the cells, leading to limitation in amino acid production, plasmid instability, and more importantly, oxidation of proteins.…”

Including dissolved oxygen dynamics into the Bt δ-endotoxins production process model and its application to process control

“…On the other hand, as stated before, a low dissolved oxygen concentration (below the critical value for the microorganisms) produces an effect known as "oxygen limitation". Therefore, it is apparent that high and low dissolved oxygen concentrations, as well as oxygen fluctuations, can be detrimental for protein expression (Konz et al, 1998).…”