protein folding

[agustin at GREEN.DFCI.HARVARD.EDU]

Dear crystallographic netters,

Simon M. Brocklehurst (smb18 at mole.bio.cam.ac.uk) wrote in <2ojbb1$9rn at lyra.csx.cam.ac.uk>:
>   The idea that x-ray or nmr structures of proteins are not the "right"
>structures is probably not correct. Globular proteins have been shown to
>have essentially the same structures in a variety of quite different
>environments.  Many enzymes have biological activity under these conditions
>etc etc.

Basically I agree since that makes it easier to work in X-ray crystallography ;-).
But it's alway good to be a little sceptical about the obtained results. I 
remember this article in Science (vol. 256, April-3-92): A Conformation of CsA 
in Aqueous Environment Revealed by the X-ray Structure of a CsA-Fab Complex. Written
by D. Altschuh et al. 
The structure of a CsA-Fab complex has been solved by X-ray analysis with a 
resolution of 2.65 A. This conformation is similar to an observed structure
of a complex CsA-CYP (rotamase) and *different* from its conformation in an
*isolated* form as determined from X-ray and NMR analysis.
Because the surfaces of CsA+CYP or CsA+Fab are *not* identical it is suggested
that the conformation of CsA (bound form) preexists in aqueous solutions -
it is not produced by interaction with the proteins.

I hope I could reflect the basic idea behind this article adding that it
important to consider the hydrophobicity of the environment when comparing
tertiary conformations.

Cheers,
	Agustin

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        Agustin de la Calle
        Dana-Farber Cancer Institute
        Harvard Medical School
        44 Binney Street, D1040
        Boston, MA 02115

        agustin at green.dfci.harvard.edu
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