We believe this site might serve you best:

United States

United States

Language: English

Promega's Cookie Policy

Our website uses functional cookies that do not collect any personal information or track your browsing activity. When you select your country, you agree that we can place these functional cookies on your device.

Our website does not fully support your browser.

We've detected that you are using an older version of Internet Explorer. Your commerce experience may be limited. Please update your browser to Internet Explorer 11 or above.

The Single Step KRX Competent Cells: Efficient Cloning and High Protein Yields

  • Print
  • Email

Abstract

We describe a new strain of Escherichia coli that has advantageous features for cloning and screening plus engineered attributes for tightly controlled protein expression. This new KRX strain is compatible with blue/white screening and can be made highly competent. In addition, KRX allows T7 RNA polymerase-based protein expression, one of the most widely used expression systems due to its well-defined promoter and the rapid elongation rate of the polymerase. In this strain, the T7 RNA polymerase gene is controlled by a rhamnose promoter. When we used the KRX strain to express firefly luciferase protein, the precise control of the rhamnose operon resulted in a dramatic induction ratio of 1,700-fold upon addition of rhamnose, whereas the leaky IPTG-inducible T7 RNA polymerase-based system in BL21(DE3)-derived strains only showed an 8- to 43-fold induction ratio, primarily due to high pre-induction levels of protein expression. Protein expression levels in KRX for three additional proteins were shown to be as high, or higher than, levels in BL21(DE3)-derived strains.

Promega Notes 94, 27–30.

Jim Hartnett, Jill Gracyalny and Michael R. Slater

Promega Corporation
Publication Date: 2006

Download Article (141 KB)