Re: Trp-Cys crosslink
John Hempel (hempel@psc.edu)
Wed, 19 May 1999 13:44:30 -0400
At 09:26 AM 5/17/99 +0000, VERNON SHOUP wrote:
>
>A few week ago, Alex Bell asked for information about non-disulfide
cross-links between proteins. The replies......... seemed to involve
cross-links occuring naturally in biological systems........... I would
like to reopen this question for cross-links formed under degradative
conditions.
>
Vernon-
Unmodified Cys and Trp can crosslink to form tryptathionine under CNBr
cleavage conditions. That is according to a posting on this network in
late '96 or else '97 (don't remember who - sorry), which gave the
Naturwissenschaften (1987) 74: 367-373 ref I posted in reply to Alex
earlier. However, that ref focuses on phalloidin, the natural source of
tryptathionine. My German is sketchy at best, but that ref does not seem
to deal with formation of this xlink under any degradative conditions. A
search of Medline just now using tryptathionine did not turn up much
fitting the bill either. With others here, I showed in a poster at Annecy
'96, before we were aware of its natural occurrence, and where we called it
cystophan, that it forms after CNBr digestion of a bacteriophage capsid
protein. (No comments received at that meeting, BTW, that this was already
known.)
To continue the question, I would be most grateful if anyone could direct
me to a paper which shows Cys-Trp xlinking after CNBr. The closest re. all
this that turned up from Medline was BBActa (1978) 533:440, formation of
~70mg tryptathionine after refluxing 3g total of cysteine and tryptophan in
6N HCl. Still a far cry from formation during CNBr of a protein. If this
is indeed known as a potential consequence of CNBr digestion, it may be
that the reason for not turning up in Medline is that others were also
unaware that there was precedence to refer to the crosslink as tryptathionine.
Regards,
John
John Hempel, PhD Ph (412) 624 0161
University of Pittsburgh FAX (412) 624 4759
Department of Biological Sciences
Pittsburgh PA 15260 email: hempel@psc.edu
http://www.pitt.edu/~biology/faculty/hempel.html