Proteins which run high on SDS-PAGE

Enrique Jose Labadan Frio - SCBC - 3421101 g3421101 at mucc.mahidol.ac.th
Sun May 19 19:15:48 EST 1996


Achim Treumann (a.treumann at dundee.ac.uk) wrote:
: Enrique, 

: I am not sure, whether I agree with you. Evans et al. have shown a while 
: ago (in the mid-eighties, I do not have the reference at hand just now, 
: email me if you really want to know) by NMR that (-Pro-Lys-) or 
: (-Pro-Glu-) repeat domains which occur naturally in many proteins have an 
: almost completely extended structure. Yet these proteins do migrate 
: significantly slower. Could this be because often many prolines go 
: together with very hydrophilic domains which bind less SDS?

Hi Achim,

This is exactly what I tried to point out in my previous message. 
Polyproline segments (binding regions for - which one is it? - one of the
many signal transduction proteins) have been shown to be linear as well as
some others (ie, keratin, collagen), but it's a well- known fact that Pros
in fewer numbers do constrain ie helical segments to conformations
described as "kinked" or "bent". 

Perhaps the NMR reference you mentioned (yes, I think everyone here will
be interested in it) dealed with trans- Pro's and not Cis-Pro's? 
Trans-Pros (omega = 180 degrees) can give lesser steric interference than
cis-Pros, and would thus accomodate Glu's and much more Lysine's at the
flanks, I would have thought... 

The hydrophilic domains which may bind less SDS may be one clue though one
can also argue that Pro's occur more on loops than in domains themselves. 

However I admit this discussion is pretty interesting. Let's keep it up
and I know I've got something new to learn everyday! :)


: Best wishes, 
: Achim

         All the best!
 
 Querix
 g3421101 at mucc.mahidol.ac.th



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