FeS cluster formation by CS bond cleavage reaction of mononuclear Fe(II) cysteine-containing peptide complexes

262

Journal of Inorganic Biochemistry

Abstracts

F e - S CLUSTER FORMATION BY C-S BOND CLEAVAGE REACTION

J17

OF

MONONUCLEAR

Fe(II)

CYSTEINE--CONTAINING

PEPTIDE

COMPLEXES T. Ueno, N. Ueyama and A. Nakamura

Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka Osaka 560, Japan In the active site of rubredoxins, an invariant peptide fragment, Cys-X-Y-Cys-Gly, has been found to ligate an iron ion.[1]

The Fe(II) peptide complexes having the specific sequence, Cys-Pro-

Leu-Cys-Gly-Val, have been studied as models of the reduced rubredoxin.

The peptide fragment

contributes to the stability of Fe(II) state with the S, S-chelation in acetonitrile. [2]

Although the Cys-

Pro-X fragment were found in not only rubredoxins but also ferredoxin, the chemical function of such a fragment remains undefined. The thermal stability of nuclear Fe(II)

mono-

cysteine-containing peptide

4

Rs

.sRp

_

CH=CN

4 as, !"sR

/F + 4 RS S -

~HX + 4 H* COY

COY

complexes was investigated in acetonitrile. We found that the mononuclear Fe(II) cysteine

eooc

jFe /HX RS S v / X

XNH

[F

S4I(SR)4

NHX

+ 4

+ Y

2RSSR

COY

-containing peptide complexes produce [Fe4S4] FIGURE 1. Proposedmechanismof Fe-S cluster formation (R; Ph-Ctt2-OCO42ys-OMe,X; Ph-CH2-OCO-,Y; -OMe ) cluster without the addition of inorganic sulfide.

The

ESI-MS

spectral analysis

TABLE I. The formation of lFe4Sd duster from Fe(l]) indicated the formation of [Fe4S 4] cluster and complexesof cysteine-containingpeptidesin acetonitrile. sulfide from the Fe(II) complexes in Complexes Yieldof [Fe4S,1 cluster(%) acetonitrile at 60 cC. The results suggest that [Fen(Z-cy s-OMe)4] (1) 65 the S--C bond cleavage of a cysteinyl residue [Fen(Z-cy s-Gly-OMe)4](2) 76 32 ligating to iron(II) serves an inorganic sulfide [Fen(7__mys-Pro-OMe)4](3) 84 (FIGURE 1). The yield of the cluster from IFeu(Z-cy s-Gly-Leu-OMe)4](4) IFen(Z-c~,s-Pm-Leu-OMe)41(5) 19 several peptide complexes is shown in TABLE Reaction conditions: underAr, aoetonitrilesolution of the FeOD I. The results indicate that the peptide complex(lmM) is kept at 60 °C for 2 h, andthen1000equivofPhSH is ~ and the yieldof [Fe4Sd clusteris analyzedby UV-vis. sequence, Cys-Pro-Leu, represses the C-S bond cleavage.

The presence of NH(Leu)---

S(Cys) hydrogen bond disturbing the cleavage was detected by 2H NMR.

The preferred

conformation of Cys-Pro-Leu by specific NH---S hydrogen bond plays an important role in the enhancement of the Fe(Cys) 4 stability in the momonuclear Fe(II) peptide complex. 1. M.K. Johnson,in EncyclopediaoflnorganicChemistry,R. B. King,Ed., John Wiley& Sons, New York, 1994,p.1896 2. N. Ueyama,Wei-YinSun and A. Nakamura,lnorg.Chem., 3 1, 4053 (1992).