You dont say whether the molecules in the native cell form a dimer - if
so I would search with that (you may need to turn off the packing search)
Or whether there is a pseudo translation vector in the mutant form..
Or what the data analysis graphs from TRUNCATE show - are they "normal"?
Eleanor
Demetres D. Leonidas wrote:
> Dear all,
>
> we have encountered a problem in solving one mutant structure. The
> mutant protein crystallizes in the same space group as the native (C2)
> but the unit cell dimensions are different. These for the native
> structure are 101.2 33.1 73.4 90 90.3 90 and for the mutant 160.4 32.3
> 107.0 90 125.7 90. As a result the mutant structure has four
> molecules in the asymmetric unit while the native had two. When we run
> molecular replacement all programs (CNS, molrep, and amore) find only
> two molecules. Phaser finds four but when we try to refine the Rfree
> does not drop below 0.44 if we use four molecules and 0.53 if we only
> use two no matter how well we built the molecule and regardless of any
> addition of water molecules (the resolution of the data is 2.1). The
> interesting thing is that in the electron density map we can clearly
> see density for a substrate analog that was included in the
> crystallization media. Do you thing that we have a case of twinning
> here ? We have to mention that Tod Yates served did not indicate any
> perfect merohedral twinning (partial merohedral twinning for this
> space group is not possible).
>
> We would appreciate any comments
>
> Many thanks
>
> Demetres
>
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