sci-chemistry
jlec@gentoo.org
It has been estimated that more than 20% of the proteins in the BMRB are
improperly referenced and that about 1% of all chemical shift assignments are
mis-assigned. These statistics also reflect the likelihood that any newly
assigned protein will have shift assignment or shift referencing errors. The
relatively high frequency of these errors continues to be a concern for the
biomolecular NMR community. While several programs do exist to detect and/or
correct chemical shift mis-referencing or chemical shift mis-assignments, most
can only do one, or the other. The one program (SHIFTCOR) that is capable of
handling both chemical shift mis-referencing and mis-assignments, requires the
3D structure coordinates of the target protein. Given that chemical shift
mis-assignments and chemical shift re-referencing issues should ideally be
addressed prior to 3D structure determination, there is a clear need to develop
a structure-independent approach. Here, we present a new structure-independent
protocol, which is based on using residue-specific and secondary
structure-specific chemical shift distributions calculated over
small (3–6 residue) fragments to identify mis-assigned resonances. The method
is also able to identify and re-reference mis-referenced chemical shift
assignments. Comparisons against existing re-referencing or mis-assignment
detection programs show that the method is as good or superior to existing
approaches.