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significant information can be extracted from both. However the hinge population of the
Hinge Atlas is different from that of the computer annotated set, albeit with much lower
significance. We argue that one of the two sets should therefore be preferred for
statistical studies. The preferred set should be the Hinge Atlas since the computer
annotated set contains numerous annotations which are slightly different from the correct
and visually verifiable hinge location.
Similarity within morph pairs
We next asked the question, do the morphs in the Hinge Atlas reflect intrinsic flexibility
of the protein, or is the apparent conformational change the result of sequence
differences between the two structures in the pair? That is, do the morphs display
motions observable in a single protein, or do they instead represent evolutionary change?
To answer this we counted the number of times both structures in the morph came from
the same vs different organisms. Of the 214 morphs, 123 had structures downloaded
directly from the PDB rather than uploaded by users, and also had valid source organism
data. For 109 of the 123, both proteins in the pair came from the same species, while for
14 the two proteins came from different species. Of the 14, 11 pairs were of proteins
that were somewhat related to each other (7 pairs of bacterial, and 4 pairs of mammalian),
while only three pairs were comprised of two proteins from different kingdoms. Thus the
conformational changes are likely to reflect experimentally observable motions rather
than evolutionary effects.
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