Re: [ccp4bb] O/T: can a protein which dimerizes in solution crystallize as a monomer?

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CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Re: Quikchange cloning: Insert length
From: Michael Giffin mijogiffin {- at -} GMAIL {- dot -} COM
Date: 2008-12-01

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Subject: Re: Quikchange cloning: Insert length
From: Dima Klenchin klenchin {- at -} FACSTAFF {- dot -} WISC {- dot -} EDU
Date: 2008-12-01

Subject: Re: O/T: can a protein which dimerizes in solution crystallize as a monomer?
From: William Scott wgscott {- at -} CHEMISTRY {- dot -} UCSC {- dot -} EDU
Date: 2008-12-01

Yo Thierry:

The periplasmic domain of the aspartate receptor, in the absence of
ligand, 1lih, is a dimer, but crystallizes as a monomer in the sense
that there is one monomer per asymmetric unit. There is a disulphide
bond between two Cys36 that maintains it as a dimer (and indeed
reduction of this bond inhibits crystallization). Each of two ligand
binding sites spans both monomers. So based on that, the biologically
relevant form is definitely a dimer, so you can't conclude otherwise
based on the fact that it crystallizes as one monomer per asymmetric
unit. Now if it were to crystallize in a space group lacking a
crystallographic 2-fold coincident with the natural dimer axis, that
might be a different story.

When you add aspartate, it crystallizes as a dimer with only one of
two potential binding sites occupied by the ligand.

Bill

William G. Scott

Contact info:
http://chemistry.ucsc.edu/~wgscott/

On Dec 1, 2008, at 2:47 PM, Fischmann, Thierry wrote:

> Dear fellow crystallographers,
>
>
>
> This is a question which is not CCP4-related.
>
>
>
> Is anybody aware of a protein which is known to be a dimer in solution
> (say by SEC), and yet crystallizes as a monomer? Wouldn't the high
> concentration in the crystallization drop further favor dimerization?
>
>
>
> In other words, if a protein crystallizes as a monomer, can I conclude
> that it does not form biologically relevant dimers in solution?
>
>
>
> Thank you in advance for your replies.
>
>
>
> Thierry
>
>
>
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CCP4bb navigation

CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Re: Quikchange cloning: Insert length
From: Michael Giffin mijogiffin {- at -} GMAIL {- dot -} COM
Date: 2008-12-01

Next message:
Subject: Re: Quikchange cloning: Insert length
From: Dima Klenchin klenchin {- at -} FACSTAFF {- dot -} WISC {- dot -} EDU
Date: 2008-12-01