  Shape had been intuitively recognized to play a dominant role in determining
the global motion patterns of bio-molecular assemblies. However, it is not
clear exactly how shape determines the motion patterns. What about the local
interactions that hold a structure together to a certain shape? The
contributions of global shape and local interactions usually mix together and
are difficult to tease part. In this work, we use symmetry to elucidate the
distinct roles of global shape and local interactions in protein dynamics.
Symmetric complexes provide an ideal platform for this task since in them the
effects of local interactions and global shape are separable, allowing their
distinct roles to be identified. Our key findings based on symmetric assemblies
are: (i) the motion patterns of each subunit are determined primarily by
intra-subunit interactions (IRSi), and secondarily by inter-subunit
interactions (IESi); (ii) the motion patterns of the whole assembly are fully
dictated by the global symmetry/shape and have nothing to do with local iESi or
IRSi. This is followed by a discussion on how the findings may be generalized
to complexes in any shape, with or without symmetry.
