Hi everybody
Can anyone educate me about structural/residue disorder for conceptual clearance?
I have characterized a protein containing multiple subunits. In the active site of each subunit, a terminal carboxylate group on reaction intermediate presents a different configuration with clearly electron density support. The structural superposition of these subunits clearly shows that the residues from each active site are invariant (rmsd 0.26 Ang), except this carboxylate group with alternating configuration. Further structural superposition of this model against other available structure homologs indicates the active site is also invariant( rmsd. 0.76 ~ 1.02 Ang). The torsion anglea of the carboxylate group vary from 16 degree, 56 degree and then to 89 degree. It may be too good to believe it even if the electron density is very clear here.
In attached figure, the electron density is scaled to 1.0 sigma and the resolution of this model is 1.6 Ang.
Since such alternating configuration can represent the tautomerization in chemistry, shall I consider such configuration difference as a disorder or real configuration alternation?
Thanks,
Kevin
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