Hi Phil,
Must you tag your protein? Have you tried to express it without a tag? Perhaps you can purify the un-tagged protein with a series of chromatographic (or other) steps - particularly if it expresses well.
Eric
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Eric T. Larson, PhD
Biomolecular Structure Center
Department of Biochemistry
Box 357742
University of Washington
Seattle, WA 98195
email: [log in to unmask]
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On Wed, 23 Feb 2011, Philipp Ellinger wrote:
>Dear all,
>
>I have a question concerning removal of a his-tag sequence.
>We have crystallized a protein with an important feature at the C-terminal part of the protein.
>Unfortunately, we cannot express it with a N-terminal his-tag, only with a C-terminal his-tag.
>
>Therefore we are looking for a protease which cleaves off the sequence without leaving any extra amino acid on the C-terminus of our
>protein. Meaning we obtain really the wild type protein.
>Does anyone know about a protease or cleavage site which is completely removed?
>
>
>Many thanks in advance
>
>Phil
>
>
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