First, a picky comment on nomenclature...
CheY is not a beta/alpha barrel, it is an open beta sheet with helices
packed against both sides. See the book by Branden and Tooze, or look
up a barrel protein. Aldose reductase, or aldehyde reductase, or the
classic triose phosphate isomerase (TIM barrel) come to mind. The
nomenclature can be even more confusing. 'Doubly-wound sandwich' for
example, doesn't sound very appetizing.
Next, a few comments on the model...
The model could perhaps use some additional work. Note the Phe side chains
exposed to solvent, where they prefer not to be (Phe 48, Phe 102). Note the
helix which has its hydrophobic side exposed to solvent (Ile 88, Pro 89, Met
90, Val 92, and Ille 95). A minor point: Asp 87 at the start of that helix
probably provides an H-bond to the main-chain N of Met 90, which is otherwise
unsatisfied due to the fact that it is near the start of the helix.
I would try to adjust the model to put the hydrophobic face of that helix
on the inside of the protein, and the face which is mostly Ala on the
surface. Or is the situation the same for cheY (confession: I haven't
looked!)? Or do you expect a hydrophobic surface there to be involved in
protein-protein or domain-domain interactions?
Maybe we can all be part of the first global effort to produce a correct model
over the web!! Zounds, this is exciting!!
Surfs Up! Pete / Uppsala