Hi Lisa, hi all,
Please do not discard the alternative method(s) of "conventional" heavy
atoms. Co-crystallisation or heavy-atom containing mother liquor soaks.
You may remember that "monster" complexes have been solved in the past
by such methods, and sometimes there are difficulties in crystallising
the Se-Met version of a protein (the "native" protein gives crystals,
the Se-Met version does not). And there is still some work going on
regarding the development of novel (lanthanide-based) heavy-atom
compounds that may provide both isomorphous and anomalous differences,
the anomalous signal being extremely useful in the case of lanthanides
and can be used "on its own" to solve 3D structures (one can then go
back to the structure of the "native" macromolecule or complex if need be).
See e.g. Talon, R. et al. (2011), J. Sync. Rad. 18, 74-78 (PMID: 21169697)
and
http://www.natx-ray.com/products/catalogue_consum_CSM002.html
HTH,
Fred.
F.M.D. Vellieux (B.Sc., Ph.D., hdr)
Institut de Biologie Structurale J.-P. Ebel CEA CNRS UJF
LBM/ELMA
41 rue Jules Horowitz
38027 Grenoble Cedex 01
France
Tel: +33 (0) 438789605 (direct line), +33 (0) 663482891 (mobile phone)
Fax: +33 (0) 438785494
e-mail: frederic.velli...@ibs.fr
LISA wrote:
Hi all,
My work is to solve huge complex containing 4 different proteins and
total molecular weight is about 300 KD. I can purify the complex by
co-expression them in E.coli. This complex contains 8 protein A, 2
protein B and 1 protein C and D. protein B and protein C have
homology structures deposited in PDB database. No homology structure
available for protein A and D, which contribute 60% of the whole
molecular weight for the complex.
Now I am trying to find a way to solve the phase of this
complex. I am thinking of use sad or mad with se-Met. There total
111 Met residues in this complex. Is it possible to solve this complex
by se-Met? Does someone have experience to solve huge complex
structure with se-met? It is also very welcome for all the suggestion.
Thank you.
All the best,
Lisa
