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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 25, Number 10
BKCSDE 25(10)
October 20, 2004 

Tandem Mass Spectrometric Evidence for the Involvement of a Lysine Basic Side Chain in the Coordination of Zn(II) Ion within a Zinc-bound Lysine Ternary Complex
Sunghyun Yu, Sunyoung Lee, Gyusung Chung, HanBin Oh*
Tandem mass spectrometry, Zinc ion, Lysine amino acid, Metal ion coordination, Binding structures
We present the tandem mass spectrometry applications carried out to elucidate the coordination structure of Zn(II) bound lysine ternary complexes, (Zn+Lys+Lys?H)+, which is a good model system to represent a simple (metallo)enzyme-substrate complex (ES). In particular, experimental efforts were focused on revealing the involvement of a lysine side chain ε-amino group in the coordination of Zn2+ divalent ions. MS/MS fragmentation pattern showed that all the oxygen species within a complex fell off in the form of H2O in contrast to those of other ternary complexes containing amino acids with simple side chains (4-coordinate geometries, Figure 1a), suggesting that the lysine complexes have different coordination structures from the others. The participation of a lysine basic side chain in the coordination of Zn(II) was experimentally evidenced in MS/MS for N ε-Acetyl-L-Lys Zn(II) complexes with acetyl protection groups as well as in MS/MS for the ternary complexes with one NH3 loss, (Zn+Lys+Lys?NH3?H)+. Detailed structures were predicted using ab initio calculations on (Zn+Lys+Lys?H)+ isomers with 4-, 5-, and 6-coordinate structures. A zwitterionic 4-coordinate complex (Figure 7d) and a 5-coordinate structure with distorted bipyramidal geometry (Figure 7b) are found to be most plausible in terms of energy stability and compatibility with the experimental observations, respectively.
1477 - 1483
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