Re: [ccp4bb]: Cys modification

[Jeff Taylor <JSTaylor@duke.edu>]

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Laurence Pearl wrote:
> 
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> What you have is probably cysteic acid, which is the terminal oxidation
> product of cysteine. Replace the SH with SO3 and you will probably fit the
> density rather well.
> 
> Laurence Pearl

I've also been wondering about extra density that I see near the two
cysteines in the model I'm working on.  The data are up to 1.7A and were
collected at 100K.  Replacing the SH with SO3 does not fit well, in
either case.  The extra density is to one side of the sulfur and I
currently have it modeled as a magnesium ion.  Water doesn't fit well
either, as it can't get close enough.

Is this common?  I checked a sub set of the pdb and did not find any
metal ions near cysteines.

Jeff Taylor
-- 
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Dr. Jeffrey S. Taylor       Duke University Medical Center
Department of Biochemistry  Box 3711, Nanaline Duke Bld  
Phone (919) 681-5266        Durham, NC 27710