Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Transport of the Cu(II) Bound with Histidine-Containing Tripeptides to Cysteine. Coordination Mode and Exchangeability of Cu(II) in the Complexes
Akira HanakiNobuo IkotaJun-ichi UedaToshihiko OzawaAkira Odani
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2003 Volume 76 Issue 11 Pages 2143-2150

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Abstract

The transport of Cu(II) complexed with histidine-containing tripeptides (Cu(HiL), L = HisGlyGly (i = 2), GlyHisGly (i = 1), and GlyGlyHis (i = 2)) to cysteine was examined by a stopped-flow spectrophotometric method. The S → Cu(II) charge transfer (LMCT) bands at 335 nm and 390 nm were used as probes for tracing the reaction. Primarily formed was the ternary Cu(H−1L)(Cys) complex. The rate of the Cu(H−1L)(Cys) formation depended on the affinity of Cu(II) for the donor atoms at the fourth binding site of Cu(H−2L). Cu(H−1L)(Cys) subsequently reacted with free Cys to yield a binary complex, Cu(Cys)2. The rate of Cu(H−1L)(Cys) formation was generally faster than that of conversion from Cu(H−1L)(Cys) to Cu(Cys)2. An exception was found in the reaction with Cu(H−2GlyGlyHis), where the relation k1+ < k2+ existed. The ternary complex, Cu(H−1HisGlyGly)(Cys), was too labile to be detect by the conventional stopped-flow methods. Probably, Cu(H−1HisGlyGly)(Cys) upon forming changed spontaneously to Cu(HisGlyGly)(Cys), in which the N-terminal His residue coordinated to the Cu(II) via the amino and imidazole nitrogens, and rapidly changed to Cu(Cys)2.

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© 2003 The Chemical Society of Japan
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