Protein folding and Mr estimates

Peeter Toomik peeter.toomik at ut.ee
Fri Jan 23 05:07:00 EST 1998

There is nothing new, and there is nothing to do with protein folding
because everything must be completely unfolded after boiling with SDS and
mercaptoethanol. But some cystein residues may get oxidized again during
electrophoresis, so you may try alkylation with e.g. iodoacetamide or
vinylpyridine. Sometimes it may help, but sometimes your protein may even
polymerise during SDS/mercaptoethanol treatment under commonly accepted
We are currently working with a cysteine-rich protein, and it does
polymerise when treated with iodoacetamide. We have some preliminary
hypotheses about the chemical reactions which may occur, but nothing is
clear yet.

Peeter Toomik
Tartu University
Institute of Molecular and Cell Biology

Cormac Shaw wrote:

> Hi folks,
> Semi-hypothetically speaking, what's the likelihood of this?:
> Two similar enzymes with essentially the same polypeptide chain length
> and amino acid composition but with different folding conformations.
> Niether are glycosylated.
> BUT the two have apparent relative molecular masses
> of 74,000 and 79,000 on SDS-PAGE after treatment with
> mercaptoethanol.
> Is this probable/possible/crazy? Any pointers towards references of
> such occurances and/or comments very welcome. Maybe I'm just tired.
> Cormac.
> ________________________________________________________________________
> Cormac Shaw, BSc,                 |
> Dept. of Industrial Microbiology, |  mailto:Cormac.Shaw at ucd.ie
> University College Dublin,        |   phone: +353 (1) 706 1307
> Dublin 4, Ireland                 |     fax: +353 (1) 706 1183
> ------------------------------------------------------------------------
> "Under the most rigorously controlled conditions of pressure,
> temperature, volume, humidity, nutrients and other variables,
> the organism will do as it pleases."
> ________________________________________________________________________

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