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Re: [ccp4bb]: questions on dimers in crystal packing

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Rongjin Guan wrote:
> Sorry this is not a ccp4 question.
> Can anybody give some hints on the following questions?
>             1. Can one molecule form more than 1 kind of dimers
>                in different crystallization conditions?

i would be tempted to check all symmetry related molecules in the vicinity to make sure
that you don't have a repeating dimerisation pattern in both crystal forms... the dimer is
not formed necessarily between closest subunits... i have had dimers at different
catalytic states within the same au but have not heard of different association motifs...
had however one crystal form which contained two molecules in the au that i though were
the dimer and an extra crystal form proved that the molecular unit was actually formed
along a crystallographic two fold...

>             2. If the answer is "yes", is there any possibilities
>                that there is a dynamic equilibruim between them, and
>                what we see in the crystal structure is the main
>                dimeric form or the favorite dimer form?
>             3. what are the main factors controling the dimer formation?
>             4. Can the dimer formed in crystals reflect the situation in 
> body
>                 if it is known to function as dimers biologically?

i would guess that, if your protein runs as a single species on a native gel and appears
monodisperse in dls it probably is only one dimer form...
would be tempted to check also the crystal contacts around each form... maybe one is
forced through extensive interactions with symm. related residues...

good luck...

>             any hints and clues will be greatly appreciated.
>             Rongjin
> -- 
> Rongjin Guan, Ph.D.
> Center for Advanced Research in Biotechnology
> 9600 Gudelsky Drive
> Rockville MD, 20850
> Tel: 301-738-6210
> Fax: 301-738-6255

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