Synthetic models for the zinc sites in the methionine synthases

S J Chiou; J Innocent; C G Riordan; K C Lam; L Liable-Sands; A L Rheingold

doi:10.1021/ic000505q

Synthetic models for the zinc sites in the methionine synthases

Inorg Chem. 2000 Sep 18;39(19):4347-53. doi: 10.1021/ic000505q.

Authors

S J Chiou¹, J Innocent, C G Riordan, K C Lam, L Liable-Sands, A L Rheingold

Affiliation

¹ Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA.

PMID: 11196931
DOI: 10.1021/ic000505q

Abstract

The syntheses and molecular structures of a series of tetrahedral zinc complexes designed to model the active sites in Escherichia coli methionine synthases are reported. [PhTttBu]ZnBr (PhTttBu = phenyltris((tert-butylthio)-methyl)borate) was prepared and characterized crystallographically to provide entry into [S3]ZnX complexes. Metathesis with KSPh yielded the phenylthiolato complex, [PhTttBu]Zn(SPh), which represents a structural mimic of the homocysteine ligated form of the enzyme. Alternatively, [S2N]ZnX (X = Br, CH3, SPh) species were prepared using the new mixed-donor ligands, [Ph(pz)BttBu] (phenyl(pyrazolyl)bis((tert-butylthio)methyl)borate) and [Ph(pztBu)BttBu] (phenyl(3-tert-butylpyrazolyl)bis((tert- butylthio)methyl)borate). Protonolysis of [Ph(pztBu)-BttBu]Zn(CH3) by PhSH in toluene yielded [Ph(pztBu)BttBu]Zn(SPh), a synthetic analogue of the homocysteine ligated form of cobalamin-independent methionine synthase (Met E). The average Zn-S bond distance in [Ph-(pztBu)BttBu]Zn(SPh) of 2.37 A compares well with the EXAFS-derived distance of 2.31 A found in the homocysteine-bound form of Met E.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / chemistry*
Models, Chemical
Molecular Structure
Zinc / chemistry*

Substances

5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase
Zinc