Selective 'unlabeling' of amino acids in fractionally C-13 labeled proteins: An approach for stereospecific NMR assignments of CH3 groups in Val and Leu residues
Hs. Atreya et Kvr. Chary, Selective 'unlabeling' of amino acids in fractionally C-13 labeled proteins: An approach for stereospecific NMR assignments of CH3 groups in Val and Leu residues, J BIOM NMR, 19(3), 2001, pp. 267-272
A novel methodology for stereospecific NMR assignments of methyl (CH3) grou
ps of Val and Leu residues in fractionally C-13-labeled proteins is present
ed. The approach is based on selective 'unlabeling' of specific amino acids
in proteins while fractionally C-13-labeling the rest. A 2D [C-13-H-1] HSQ
C spectrum recorded on such a sample is devoid of peaks belonging to the 'u
nlabeled' amino acid residues. Such spectral simplification aids in unambig
uous stereospecific assignment of diastereotopic CH3 groups in Val and Leu
residues in large proteins. This methodology has been demonstrated on a 15
kDa calcium binding protein from Entamoeba histolytica (Eh-CaBP).