Luc CAMOIN wrote:
> Dear Netters,
>> I purified a recombinant protein from E Coli. The N-terminal sequence and
> Mass spectrometry experiments show that the initial methionine is eliminated
> in 90% of the purified protein.
>> Does anyone have any explanation about this phenomenon?
>
It's the effect of the second residue. See
Hirel et al, (89) PNAS 86, 8247-8251
Briefly, small uncharged second residues (e.g. glycine, alanine) result in
efficient removal of N-terminal methionine, while large, charged or aromatic
residues result in inefficient removal of methionine. For those in-between the
effectiveness of removal may depends on fermentation conditions.
>> Thanks in advance
>> Luc CAMOIN
>> --
> Luc CAMOIN
> Tel:+33 1 40 51 64 98
> Fax:+33 1 40 51 72 10
> Institut Cochin de Génétique Moléculaire / Groupe Chimie des Protéines
> Laboratoire d'Immuno-Pharmacologie Moleculaire / CNRS UPR 415
> 22 rue Méchain
> 75014 Paris France
> Internet: http://www.cochin.inserm.fr/upr415/UPR415E2.htm>
