QUESTIONS: alpha-helix "signals" in proteins

Rafael N Szeinfeld szeinfel at FOX.CCE.USP.BR
Thu Jul 14 08:51:30 EST 1994

On 13 Jul 1994, Cornelius Krasel wrote:

> Joshua Cherry (cherry at watneys.med.utah.edu) wrote:
> [about the speed of protein folding]
> : I wouldn't say that fast folding MUST be sequence independent just 
> : because "all" proteins fold fast.
> What does "fast" mean in the context of protein folding? I am not a
> structural biologist (heaven forbid), but the beta-2-adrenergic receptor
> needs apparently about 30 min to be correctly folded and/or processed
> (B. K. Kobilka, JBC 265, 7610-7618, 1990). Admittedly this is a
> membrane protein, but nevertheless the process does not seem to be
> "fast" :-)
> --Cornelius.
	Fast means in my point of view that the folding process happens in
a period of time compatible with the need for that folded protein in the
cell. What I meant when I said that the process is sequence independent is
that what gives the major contributions to decrease the portion of
configurational space to be searched are excluded volume effects from the
side chains. of course the volume of a side chain is sequence dependent
but this is a property of all aminoacids not the same happens with the
hydrophobic effect where not all the aminoacids are hydrophobics. This
idea is not yet clear to me so I'd like you to discuss it.

	Sincerly yours,
			Rafael Iosef Najmanovich Szeinfeld

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