> moreaut@univ-tours.fr writes:
>
> > as to the quaternary structure, I would suggest:
> > the symetrical arrangement of subnits in a protein
>
> should we have to be so restrictive as to include the word "symetrical" in
> this definition. Are arrangements of subunits always symetrical? (I know
> this is what the Monod-Wyman-Changeaux model of allosteric transitions
> states, but...)
>
> Maybe someone else can answer this question: "Are arrangements of subunits
> always symetrical?"
I seriously doubt this. Look at the quaternary structure of a heterotrimeric
G protein, consisting of an alpha-, beta-, and gamma-subunit. The structures
of beta and gamma are not yet known, but it is highly unlikely that they
will form a symmetric body around the alpha part.
I think what the original poster envisaged was the symmetrical arrangement
of multisubunit proteins which consist of multiple copies of the same
subunit. Not very surprisingly, these are often symmetrical (for reasons
why, see the 3rd ? chapter of Alberts et al.).
--Cornelius (a student :-)
-- /* Cornelius Krasel, Abt. Lohse, Genzentrum, D-82152 Martinsried, Germany */ /* email: krasel@alf.biochem.mpg.de fax: +49 89 8578 3795 */ /* "Science is the game you play with God to find out what His rules are." */