Dear Modh,
I agree with Paul, this is covalente modification of Cys. I would try
cysteine persulfide (CSS), and cysteine sulfenic acid (CSO).
In COOT, center on this cysteine, and then do: Calculate -> Modelling ->
Replace residue; write CSS (or CSO), save the coordinates and refine.
HTH,
Jose
---
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* Membrane Protein Crystallography Laboratory *
* Instituto de Tecnologia Quimica e Biologica Antonio Xavier *
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Date: Thu, 17 Mar 2022 17:37:17 +0000
From: Mohd Syed Ahangar <mohdsye...@gmail.com>
Subject: Cysteine-S-Iodine interaction
Hi CCP4BB members.
I have been doing some protein crystal soaking with some covalently
binding
fragments and in one structure I have got an extra density on Cysteine
but
that density doesn't match with the expected fragment. The fragment was
in
the form of iodide salt. when I fit the Iodine in the density, it
fitted
fairly well than any other possible chemical entity. From the density
map
it looks like something is covalently bound to Cysteine.
Now my question is, can a sulphur atom of Cysteine have such an
interaction
with Iodine. The distance between S and Iodine is 2.76A in this case as
shown in the attached figure.
I would be grateful if someone can shed some light on this.
Thank you in advance.
--
Dr. Mohd Syed Ahanger,
Faculty of Biological Sciences,
University of Leeds, Leeds, UK.
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