Dear Leonard,
Have a look at the work of Elena Cabezon, Martin Montgomery, Andrew
Leslie and John Walker. They solved a structure of two F1-ATPase
"molecules" linked by a dimeric inhibitor subunit; if I understand
both cases correctly there are similarities.
Cabezón E, Montgomery MG, Leslie AG, Walker JE.
The structure of bovine F1-ATPase in complex with its regulatory protein IF1.
Nat Struct Biol. 2003 Sep;10(9):744-50.
Greetings,
Mark
Quoting Leoanrd M Thomas <[log in to unmask]>:
> To clarify a bit, the protein is not cyclic, it is two of the wild type
> protein molecules joined together by a short peptide linker creating a
> "new" protein.
>
> Here is my attempt at an ascii sketch,
>
> 2-fold 2-fold
> __
> ( ) ( ) Linker
> ( ) ( )
> ( ) ( )
> ( ) ( )
> ( ) ( )
> Linker (__) ( )
>
> When looking at the crystal imagine half the unit cells of the crystal
> have the linker on the "bottom" of the protein and the other half have it
> on the top. The modified protein crystallizes in the same space group and
> unit cell as the wild type.
>
> I am just not sure how to describe it or for that matter refine the
> system. One half of the new molecule is in the ASU while the other half
> is related by the crystallographic two fold.
>
> We have run the usual checks for twining and making sure we are in the
> proper space group. We would not have this problem if we ignored the
> higher symmetry, of course it would be wrong. It refines nicely in both
> the space groups but the overall processing statistics really indicate
> that it is in the higher space group.
>
> Cheers,
> Len
>
>
>
> Leonard M. Thomas Ph.D.
> Director, Macromolecular Crystallography Laboratory
> Howard Hughes Medical Institute
> California Institute of Technology
> Division of Biology
> 1200 E. California Blvd. MC 114-96
> Pasadena, CA 91125
> 626-395-2453
> [log in to unmask]
> http://www.br.caltech.edu/cmclab
>
|