Insulin can take very different structures for 20% of the residues in
different conditions, and there are several examples of "T3R3"
hexamers, with one "T" and one "R" in the asymmetric unit. There are
even observations of the transformation occurring within the crystal,
which looked battered but still diffracted to some extent. Examples
are: 2tci 3mth 1mpj
Eleanor Dodson
On 30 January 2014 11:06, Bernhard Rupp <[log in to unmask]> wrote:
> There is one additional point perhaps worth making: As already noted in the
> thread, if you have a NCS homo-oligomer, the different copies in general
> have different environment, and proper inspection of the contacts reveals
> the details. On multiple occasions during inspections and review I have
> noticed that such is not always interpreted or welcome as a functionally
> necessary manifestation of the plasticity of the protein in question. In
> case of binding sites, in contrast it occurs that the 'best' one where a
> ligand actually exists or assumes a pose/environment perceived as useful for
> the proposed hypothesis is picked as the representative (figure), and from
> there the story evolves. This misses the point, and somewhat reeks of
> confirmation bias (the neglect of negative or 'unsuitable' results) leading
> straight down the road to scientific serfdom in terms of becoming a slave of
> one's own (pre)conceptions....
>
> Best regards, BR
>
>
> On Wed, Jan 29, 2014 at 10:24 AM, Kay Diederichs
> <[log in to unmask]> wrote:
>>
>> Hi Shane,
>>
>> some crystal forms of trimeric AcrB (a multi-drug resistance secondary
>> transporter) have 3 (or 6) monomers in the ASU and these are substantially
>> different, which suggests how the protein functions.
>> One reference is e.g. Seeger et al. (2006) "Structural Asymmetry of AcrB
>> Trimer Suggests a Peristaltic Pump Mechanism " Science 313, 1295-1298
>> DOI: 10.1126/science.1131542 (sorry for the self-plug!)
>>
>> best,
>>
>> Kay
>>
>>
>>
>> On Mon, 27 Jan 2014 13:08:33 -0500, Shane Caldwell
>> <[log in to unmask]> wrote:
>>
>> >Hi ccp4bb,
>> >
>> >I'm putting together a talk for some peers that highlights strengths and
>> >weaknesses of structural models for the outsider. For one point, I'd like
>> >to find some examples of proteins that show very different conformations
>> >between different copies in the ASU. One example I know of is c-Abl
>> > (1OPL),
>> >which crystallizes with both autoinhibited and active forms in the ASU,
>> >with dramatically different domain organization. I'd like to find some
>> >additional examples - can anyone suggest some other structures that have
>> >multiple copies with large structural variations?
>> >
>> >Thanks in advance!
>> >
>> >Shane Caldwell
>> >McGill University
>> >
>
>
>
>
> --
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> Bernhard Rupp (Hofkristallrat a. D)
> 001 (925) 209-7429
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