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RE: [ccp4bb]: stucture factor calculation

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Just for clarity:

It is not uncommon for active site residues to be in "weird" regions of
the PHI/PSI plot; when one thinks that the enzyme has to modify the
geometry of the substrate for the reaction to occur, part of the strain is
taken by active site side residues which are not in the lowest energy

Further, mobile regions, disordered loops etc often show residues in these
"disallowed" regions. The reason there is different: there is simply no
(or very poor) density for these regions; the crystallographer builds the
model into poor density (although he/she knows that the chain goes
there) and the refinement programs do not manage to fix the geometry. Such
regions also have very high B factors, their presence in the model simply
indicates the fact: "the protein goes through there".

What is worrysome is if neither of the above applies.



s-mail: F.M.D. Vellieux (B.Sc., Ph.D.)
        Institut de Biologie Structurale J.-P. Ebel CEA CNRS UJF
        41 rue Jules Horowitz
        38027 Grenoble Cedex 01
Tel:    (+33) (0) 438789605
Fax:    (+33) (0) 438785494
e-mail: vellieux@ibs.fr
 Don't even think of asking me: "I would              Het leven is genieten
  if I could, but I can't" (L.R., 1998)               (to live is to enjoy)