Formation of Co(II), Ni(II), Zn(II) complexes of alternative metal binding heptapeptides and nitrilotriacetic acid: Discovering new potential affinity tags

Using electrospray ionization-ion mobility-mass spectrometry (ESI-IM-MS) a new series of alternative metal binding-5 (amb5) heptapeptides that provide various combinations His, Cys and Asp as potential binding sites are compared for their relative formation complexes with the ions Co(II), Ni(II) Zn(II). These amb5 peptides have general primary structure acetyl-Aa1-Aa2-Gly3-Pro4-Tyr5-Aa6-Aa7, where Aa1,2,6,7 four amino acids include Cys, and/or sites. The study includes two polyhistidine heptapeptides; His-tag Pro4, because they represent widely applied His affinity tag used in expression cloning purification recombinant proteins immobilized chromatography (IMAC). We compare these amb5+M(II) amb5+M(II)+NTA complexes, M = Co, Ni, or Zn, NTA is nitrilotriacetic acid model IMAC column. Overall, results show inclusion at positions 1, 2, 7; i.e., ac-Asp1-Asp2-Gly3-Pro4-Tyr5-Aa6-Asp7, generally favors amb5+Ni(II) amb5+Ni(II)+NTA while 2 6; ac-Aa1-Cys2-Gly3-Pro4-Tyr5-Aa6-Cys7, Aa1 Asp, amb5+Zn(II) complexes. comparison competition between Zn(II) forming showed ac-Asp1-Asp2-Gly3-Pro4-Tyr5-His6-Aa7, Aa7 were most selective complex. Collision-induced dissociation single negatively-charged [amb5+Ni(II)+NTA]− shows it competitively dissociates into [amb5−3H+Ni(II)]− [NTA−3H+Ni(II)]− doubly-charged [amb5+Ni(II)+NTA]2− complex [amb5J−H]−, indicating realistic mimics inside an