[Myotox] SDS AUC update

[Bruno Lomonte]

I see Borries... agree

I found this 2007 paper that perhaps gives us important clues on this 
phenomenon of SDS-toxin interaction?

the authors put forward the idea that SDS 'simulates' the effect of 
phospholipid interactions on the protein, and that this would have 
relevance to the membrane-damaging mechanism

please see attached

Bruno


++++



On 3/12/2020 8:12 PM, Borries Demeler wrote:
> On Thu, Mar 12, 2020 at 07:26:21PM -0600, Bruno Lomonte wrote:
>> Dear colleagues
>>
>>
>> thanks for running these new experiments, and finding such interesting
>> results!
>>
>>
>> so this dimerization induced by SDS would explain the appearance of a smear
>> around the dimeric value in such electrophoretic analyses?   and this would
>> support that under physiological conditions the toxin would be a monomer,
>> the dimer being an artifact of crystallization perhaps? I am not sure if I
>> am interpreting this correctly
> Dear Bruno,
> I don't think the interpretation is straightforward. SDS is having
> a strange effect on this protein, whose structural basis should be
> understood. Uchiyama's group found the same issue on their protein.
> Other than these two proteins I have never heard that SDS is causing
> proteins to dimerize. Furthermore, Myotoxin-II is highly soluble even
> at very high concentrations, it doesn't need SDS to be in solution. ALL
> proteins I know of *monomerize* when mixed with SDS, at least on SDS-PAGE
> gels. That's the exact opposite of what we are seeing here. SDS is a
> strong denaturant.
>
> I think the questions we need to answer is this:
> 1. why is the protein oligomerizing with an apparent end state (dimer or
> trimer?) when exposed to SDS? What is the structural basis for this?
>
> 2. is this behavior also observed when the protein is mixed with other
> lipids?
>
> 3. is this behavior somehow related to its toxic action, perhaps
> disrupting membranes?
>
> 4. What does the protein do when/if it binds to membranes?
>
> The Kd for oligomerization appears to be quite low. We will investigate
> this further by running in 1% (thanks, Amy, for the correction!) SDS
> again, but this time at lower concentration to see if it can push it to
> pure monomer in SDS. The process of oligomerization appears to be
> completely reversible and mass action driven.
>
>> exciting news indeed
> Yes, fascinating. Susumu Uchiyama is a good friend of mine, I didn't
> even realize he was on the paper until today, he probably did the mass
> spec and AUC analysis, which, by the way, was well done. I will ask him
> if he has any further insights into the action of SDS.
>
> Regards, -Borries
> _______________________________________________
> Myotox mailing list
> Myotox at biophysics.uleth.ca
> http://demeler7.uleth.ca/mailman/listinfo/myotox

-- 
Bruno Lomonte, Ph.D.
Instituto Clodomiro Picado
Universidad de Costa Rica
San José, 11501
COSTA RICA

bruno.lomonte at ucr.ac.cr
tel. +506  2511 7888
cel. +506  8392 0012

-------------- next part --------------
A non-text attachment was scrubbed...
Name: 2007_PLA2_BiophysChem_Bortoleto_SDS_micelles_K49.pdf
Type: application/pdf
Size: 316928 bytes
Desc: not available
URL: <http://demeler7.uleth.ca/pipermail/myotox/attachments/20200312/a4fce278/attachment-0001.pdf>