Product Class: Strain

E. coli K12 CAG597

Limit of 1 per order. Although this product is free of charge, freight charges will apply. For US customers, available via phone ordering only (1-800-632-5227). For international customers, please contact your local NEB subsidiary or distributor.
Catalog #SizeConcentration


A suspension of E. coli strain K12 CAG597 which has been grown in rich LB medium and brought to 50% glycerol. E. coli K12 CAG597 has rpoHam allele (sometimes referred to as htpRam) which encodes an amber mutant form of the sigma factor for the heat shock response. Grow by streaking out on an LB plate and incubating at 30°C.


F- lacZ(am) pho(am) tyrT[supC(ts)] trp(am) rpsL(StrR) rpoH(am)165 zhg::Tn10 mal(am)

Properties and Usage

Storage Temperature


Supporting Documents

The following is a list of Safety Data Sheet (SDS) that apply to this product to help you use it safely.
The Product Summary Sheet, or Data Card, includes details for how to use the product, as well as details of its formulation and quality controls. The following file naming structure is used to name the majority of these document files: [Catalog Number]Datasheet-Lot[Lot Number]. For those product lots not listed below, please contact NEB at or fill out the Technical Support Form for appropriate document.


  1. The strain has a temperature-sensitive amber supressor TyrT [supC(ts)] , so upon incubation at 37°C or 42°C the strain does not suppress the heat shock sigma factor RpoH. Thus it becomes deficient in expression of the heat shock proteins. Since a number of heat shock proteins affect proteolysis, this can increase the stability of foreign proteins expressed in E. coli. CAG597 is EcoK r+m+, so plasmids have to be modified (i.e., come from an m+ strain such as TB1, JM83, JM107, etc.) in order to get transformants; the transformation frequency is 10-100X down from other common strains used for recombinant DNA work.


  1. Baker, T.A., Grossman, A.D. and Gross, C.A. (1984). Proc. Natl. Acad. Sci. USA. 81, 6779-6783.
  1. When we analyze our fusion protein expression by Western blot using the Anti-MBP Monoclonal Antibody, only a small fraction of the protein is full-length, while most of it migrates close to the MBP5* marker.