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Re: [ccp4bb] Weakest protein-protein complex crystallised
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CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999
Previous message:
Subject: Re: Weakest protein-protein complex crystallised
From: Filip Van Petegem filip {- dot -} vanpetegem {- at -} GMAIL {- dot -} COM
Date: 2008-07-01		Next message:
Subject: needles not improved
From: Marta_Martínez mmartine {- at -} UNIZAR {- dot -} ES
Date: 2008-07-01


Subject: Re: Weakest protein-protein complex crystallised
From: "John A {- dot -} Newitt" newittja {- at -} COMPUSERVE {- dot -} COM
Date: 2008-07-01

At 3:28 PM -0700 6/30/08, Filip Van Petegem wrote:

>The crystal artefact is that we don't observe any binding in the
>crystal structures of a set of mutants (neither to the native site,
>nor to any other), whereas both calorimetric and
>electrophysiological data suggest there should be binding in the
>100-200nM range. The binding is abolished because of crystal
>contacts (+ crystallization conditions) for 100nM and weaker
>binders, but not for 10nM and stronger binders.

Filip:

Are you calorimetric binding measurements performed under similar
conditions (especially pH) as your crystallization condition for the
mutant proteins? We have determined in some cases that apo crystals
are due to the fact that a ligand had reduced affinity at the
non-neutral pH of crystallization, whereas initial positive binding
studies were performed at pH ~7.

- John
--




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