An improved strategy for determining resonance assignments for isotopically enriched proteins and its application to an engineered domain of staphylococcal protein A

An improved strategy for examining sequence-specific resonance assignments was used for an 8.2-kDa engineered area of the cell wall protein A of Staphylococcus aureus with emphasis on proton and nitrogen resonance assignments. The amino acid, asparagine and glutamine spin systems were determined with a combination of HCCNH-TOCSY, 2D 2QF-COSY, TOCSY and N-HSQC data. The aliphatic resonances of residue i to the amide and nitrogen resonances of residue i + 1 and their sequential connections were determined by the HCC(CO)-NH-TOCSY data. The proton and nitrogen resonance assignments for the Z-domain were identified by the HCCNH-TOCSY and HCC(CO)NH-TOCSY spectra.