Dear Siva,
Could it be that your model is one residue out of sequence? This
sure looks like a Glu to me. In fact, it looks to be a better Glu
than the current C terminal Glu.
Dale Tronrud
siva charan wrote:
> Dear All,
>
> I have solved crystal structure of a protein at 1.8 Å resolution using
> molecular replacement. Interestingly I could see extra electron density
> at the C-terminus end. The extra electron density is like split going in
> to two directions.We have checked with MS on protein in solution for
> extra residues but we did not find any extra molecular weight.
> C-terminal sequence is verified on the DNA level by DNA
> sequencing. Protein took around 30 days to crystallize, it has PEG 3350
> as precipitant, around 0.1 M of NaCl and 0.2 M bis-tris at pH 5.5. Does
> any body have idea about these crystallizing agents doing c-terminus
> modification? I am attaching a snap shot of the extra electron density.
> I would be happy to receive information about reference about main chain
> modifications in crystallization process.
>
> Kind regards &
>
> Wish you all a happy and successful new year
>
> Siva
>
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