(no subject)

William Tivol tivol at news.wadsworth.org
Fri Jun 30 15:44:30 EST 1995

Gil Prive (prive) wrote:

: Specifically, does anyone know anything about the following: 

: 1) Gln/His rich regions. Roughly twice as much Q as H, but 
: (apparently) randomly shuffled, about 25 residues long. 

: 2) strictly alternating Arg/Glu repeats, also about 25 residues long. 

: Do these ring any bells with anyone? Any guesses as to whether they have 
: a defined stucture or not? 

Dear Gil,
	Strictly a guess.  These regions must be in contact with solvent--
there's too much charge and polarity for them to be interior.  Sequence 1) pro-
bably binds to some highly negative substrate or cofactor; nucleic acids would
be my guess.  If they bind to macromolecular nucleic acids, they probably act
to hold NA for the active site to work on.  Thus they would be physically near
the active site (although they might not be near in the primary sequence).  Se-
quence 2) is too well ordered to be an accident--it must have some function.
I'd also guess that the secondary structure is specific, by which I do not mean
that it cannot be a random coil, but that it likely has the same structure in
each instance.  Possibly some structure where all the R face one way and all
the E face the other would perform some task, or possibly the ion pairs could
be in proximity (producing little electric potential) in one conformation and
changed so that one charge species is neutralized to a greater or lesser degree
in another conformation.  Good luck and please post a summary of any authorita-
tive responses (which mine is not) you get.
				Bill Tivol

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