Isolating Transcription Factors

Transcription factors are extraordinarily diverse, and any one factor represents only a tiny fraction of the protein molecules present in the cell. This page describes how one can isolate and purify such rare molecules.

Example: isolating the lac repressor

An E. coli cell contains only 10-20 copies of the lac repressor. This represents a ratio of only 1 molecule in 50,000 protein molecules in the cell.

Link to a discussion of the lac repressor

However, the specificity of the lac repressor for the DNA sequence of the operator provides a mechanism for fishing it out of the mixture.

The procedure:

This technique is called affinity chromatography. Many eukaryotic transcription factors have also been isolated and studied by this method.

Link to a discussion of eukaryotic transcription factors.
Link to another example of affinity chromatography.
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17 February 2011