QUESTIONS: alpha-helix "signals" in proteins

Dr. Dennis Goode GOODE at ZOOL.UMD.EDU
Mon Jul 18 15:59:44 EST 1994


 RES4010 at HUSKY1.STMARYS.CA ("W.  Klonowski", Vladimir) wrote
in Message: <01HEGO4MYB7A8WWF5W at HUSKY1.STMARYS.CA>
>(most deleted) ---we think that the proteins
> with short half-time "work" in states far from thermodynamic equilibrium
> (cf. Klonowska and Klonowski, BioSystems 21 (1988) 135-139).
> 
> So, one can say that biosynthesis of such proteins is kinetically 
controlled, but for other proteins thermodynamics may prevail over 
kinetics - it depends > very much on the protein's primary structure.
> 
> During renaturation the whole chain already exists and the final structure
> is most probably thermodynamically controlled. For some proteins it may be
> the same or a very similar structure as a 'native' one. For these which form
> "Klonowski-Klonowska conformons" it will be a very 'non-native' structure, 
> these protein would never be able to get renaturated. 
> 
> BTW, if you know about proteins which have resisted all efforts of being
> renaturated, as well as about proteins with short life-time (say less than
> 30 min.) please e-mail me the information. Thank you.
> 
> Dr. W. (Vladimir) Klonowski
> res4010 at husky1.stmarys.ca

When tubulin purified at pH 6.8 is briefly transferred to pH 10.5 and 
then back to pH 6.8, it loses its ability to polymerize or assemble 
into microtubules.  Since ability to assemble is very sensitive to 
tertiary structure, we have thought this was probably due to 
inability to renature to the original 'native' conformation. Perhaps 
that systen should be investigated further.  However, tubulin assembly 
is complex in that the assembly competent subunit is a heterodimer 
of alpha and beta tubulin and a bound guanosine triphosphate is 
usually required for assembly, so a pH shift might alter other 
aspects of the system. 

This experiment was done at a concentration of tubulin well 
above the critical concentration for assembly, so it's not just a 
small reduction in the conc. of tubulin necessary to support assembly. 
However, it is possible that a small fraction of inapproriately folded 
tubulin could block further assembly.

Any thoughts about this system?

Dennis Goode
Dept of Zoology
Univ of Maryland
College Park, 20742 
Goode at Zool.umd.edu

"It's a mistake to give answers to questions that have not been asked"
    - Paul Tillich



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