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

- Protein crystallography

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- Crystallisation

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

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Subject: Re: O/T: can a protein which dimerizes in solution crystallize as a monomer?
From: "R {- dot -} J {- dot -} Lewis" r {- dot -} lewis {- at -} NCL {- dot -} AC {- dot -} UK
Date: 2008-12-02

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Subject: Offtopic: FAD enzymatic assay: a little bit more about my enzyme
From: michael nelson gnomenm {- at -} YAHOO {- dot -} COM
Date: 2008-12-02

Subject: Re: O/T: can a protein which dimerizes in solution crystallize as a monomer?
From: "Brown, Kate A" k {- dot -} brown {- at -} IMPERIAL {- dot -} AC {- dot -} UK
Date: 2008-12-02

Hi Thierry,

We have worked on a number of proteins where the oligomerisation
state differs from that found in solution. A recent example is a
project we worked on involving the HC fragment of tetanus toxin
(see Qazi et al., J Mol Biol. 2007 Jan 5;365(1):123-34) which
crystallises
as a monomer. The discovery of it multimerising was somewhat
serendipitous in that the protein (like so many these days) was
purified using a his-tag and then crystallised. We planned to use SAXS
to study proposed conformational changes and looked at the protein
on a native gel as part of our standard preparation for these
experiments.
The native gel showed the protein multimerised and the combination of
the
SAXS and excellent crystal structure from the Isaacs group led to new
ideas
about the function of the toxin.

A few points:

1. Crystallisation conditions can be very selective for different
oligomerisation
states of protein and other parameters ( e.g., pH, ionic strength,
oxidation state,
exogenous ligands,...) besides concentration can affect the equilibria
controlling
whether a protein appears to be a monomer or not as the case may be.

2. It is always worth looking carefully at native gels or other sizing
data for
any protein which is crystallised. With the great expression systems out
there using
affinity tags this sometimes gets forgotten.

3. Be aware that truncated forms of proteins (even small deletions) may
affect
oligomerisation states (we have also seen this with a membrane bound
receptor
we are working with now and I think there are other similar examples in
the literature)

best wishes,
Kate

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

Next message:
Subject: Offtopic: FAD enzymatic assay: a little bit more about my enzyme
From: michael nelson gnomenm {- at -} YAHOO {- dot -} COM
Date: 2008-12-02