Hi,
I'd like to echo Matt on the removal of N-terminus Met expressed in E. coli. For eukaryotic (esp. mammalian) proteins it is almost certain that the first Met is removed. I observed with ESIMS that about half of an yeast protein bear the first Met. With my limited experience, both E. coli and Salmonella proteins may retain their first Met in many cases. I am not sure if this removal complicates crystallization.
Yong
On 9/26/06, [EMAIL PROTECTED] <[EMAIL PROTECTED]
> wrote:
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[EMAIL PROTECTED] wrote on 09/26/2006 11:47:47 AM:
> Hi,
>
(snip)
>
> Anyone experienced such problem? Is the head of protein already cut
> during _expression_, or just lost in MALDI experiments?
>
> Yadong Yu
Dear Yaodong -
All (?) E. coli expressed proteins have their initial methionine removed
during translation by methionine aminopeptidase. This is no doubt what
you're seeing.
- Matt
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