Fresh Frozen Competent Cells

For routine subcloning, nearly every manufacturer has a repertoire of standard laboratory strains. Many companies have expanded their range of products with special-function host strains that overcome many of the critical problems encountered during cloning and maintaining non-E. coli sequences in bacteria. Stratagene has a sizable entry in the special-use bacterial strain segment. Among some of the high-efficiency strains are those for maximizing or exploiting aspects of protein expression. Th

Thomas Unger
Nov 23, 1997

For routine subcloning, nearly every manufacturer has a repertoire of standard laboratory strains. Many companies have expanded their range of products with special-function host strains that overcome many of the critical problems encountered during cloning and maintaining non-E. coli sequences in bacteria.

Stratagene has a sizable entry in the special-use bacterial strain segment. Among some of the high-efficiency strains are those for maximizing or exploiting aspects of protein expression. The TOPP, ABLE C, and ABLE K E. coli strains assist in expressing toxic or unstable proteins by limiting plasmid copy numbers. The TKB1 and TKX1 strains are engineered to have an inducible elk tyrosine kinase gene controlled by the trp promoter. When expressed, this gene phosphorylates proteins in the host strain. This feature is useful for affinity screening of libraries, for purification of SH2 domain-containing proteins, or for other strategies in which phosphorylated residues have a selective advantage.

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