Ternary Cu(II) complexes, Cu(H(-1)L)(ACys-) and Cu(H(-2)L)(ACys-); L = peptides, ACys- = N-acetyl-cysteinate. Analogous complexes to the intermediates in the transport of Cu(II) from Cu(H(-2)L) to cysteine.
The Cu(II) in Cu(H(-2)L) has been postulated to be successively transported to cysteine (Cys) as follows; Cu(H(-2)L) <==> Cu(H(-2)L)(Cys*-) <==> Cu(H(-1)L)(Cys*-) --> Cu(H(-1)L)(Cys-), where Cys*- denotes the monodentate Cys-. N-acetyl-cysteinate (ACys-) complexes Cu(H(-2)L)(ACys-) and Cu(H(-1)L)(ACys-), having similar coordination modes to Cu(H(-2)L)(Cys*-) and Cu(H(-1)L)(Cys*-), respectively, exhibited the S --> Cu(II) charge transfer absorption at 325-355 nm and the d-d absorption at 530-610 nm. A linear interrelation existed between the energies of the CD and d-d absorptions. Cu(H(-2)L)(ACys-) were in rapid equilibrium with Cu(H(-1)L)(ACys-). Upon forming the ternary complex, pK(c2) of the parent Cu(H(-1)L) was raised to more than 1.0. The formation constants (K) of the Cu(H(-1)L)(ACys-) species from Cu(H(-1)L) were bigger than those of Cu(H(-2)L)(ACys-) from Cu(H(-2)L). The linear free-energy relationship existed between the free-energy change (deltaG) and the entropy change (deltaS) for the ternary complex formation. The rate constants (k1+) for the Cu(H(-1)L)(Cys-) formation closely correlated with the K values for Cu(H(-2)L)(ACys-). The ternary complexes containing ACys are considered to be analogous complexes to the intermediates in the transport of Cu(II) from peptides to cysteine.
Hanaki
Akira
A
National Institute of Radiological Sciences, Anagawa 4-9, Inage-ku, Chiba 263-8555, Japan. b42170a@nucc.cc.nagoya-u.ac.jp
Funahashi
Yasuhiro
Y
Odani
Akira
A
D000111:Acetylcysteine / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D003545:Cysteine / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D006033:Glycylglycine / Q000737:chemistry; D007700:Kinetics; D008956:Models, Chemical; D015394:Molecular Structure; D009842:Oligopeptides / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
D009842:Oligopeptides; D006033:Glycylglycine; C060757:glycyl-glycyl-sarcosine; D003300:Copper; C035647:glycyl-glycyl-glycine; D003545:Cysteine; D000111:Acetylcysteine