Protein purification: iodoacetic acid -does it stuff up cysteines

[Cornelius Krasel]

Orak (Ross.Thomas at med.monash.edu.au) wrote:
> I have been using iodoacetic acid (IAA) as a protease inhibitor for purifying
> recombinant transcription factors.  However, someone recently told me
> that IAA works by modifying cysteine residues.  Can someone confirm this
> for me? 

That's what I have learned when I was still a student. Look up Stryer
or other biochemistry books. The alpha-C in IAA is very poor in electrons,
therefor it easily forms covalent bonds with electron-rich partners,
such as the sulfur in Cys or the N in His. These alkylation reactions
are essentially irreversible.

--Cornelius.

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