Hidden order in the GroEL-GroES-(ADP)7 chaperonin: forms, folding, and ADP-binding sites.

A molecular crystallography approach reveals the existence of a hidden order in GroEL-GroES-(ADP)(7). The new crystallographic symmetry concepts required are first illustrated for a hypothetical planar molecule. Their application to the chaperonin complex leads to molecular forms with vertices having integral coordinates (the indices) with respect to a symmetry-adapted basis and to folding points approximated by ideal C(alpha) positions with rational indices connected by integral scale-rotations, just as for the vertices of the molecular forms. The Mg(+2)-ions at nucleotide binding sites are symmetry-related in a similar way to C(alpha)'s folding points.