Important Question About AMINO ACIDS ?????
Shaun D. Black
SHAUN at JASON.UTHCT.EDU
Wed Sep 14 09:21:56 EST 1994
ybou at fox.nstn.ns.ca (Yvon Boudreau) on 13 Sep 1994 writes:
> 1.) Why are the amino acids of the "alpha" type?
> 2.) Why are they of the "levo" type?
> These questions were given to me in my grade 12 biology class.
> Help would be very much appreciated!
My reading of the scientific literature suggests that noone really knows the
answer to these questions. Probably the most important thing for a grade
12 biology class to know is that these observations are nearly inviolate
throughout all known organisms/proteins in nature.
A guess/hypothesis concerning (1) is that beta, gamma, etc. amino acids would
impart too much backbone flexibility and thus degrees of freedom to a folding
polypeptide chain. In all likelihood non-alpha amino acids in peptide
linkage would not fold. As for (2), this has been covered in an extensive
thread on Methods-and-Reagents a few months back; check the archives,
preferably by a Gopher search. Briefly, polypeptides of L-amino acids form
structures with right-handed helices, right-handed twists to beta strands,
left-handed twist to beta sheets, etc. Polypeptides of D-amino acids form
the same structures but of the _opposite_ handedness. I hope this helps you
a bit. Best regards,
= Shaun D. Black, PhD | Internet address: shaun at jason.uthct.edu =
= Dept. of Biochemistry | University of Texas Health Center, at Tyler =
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