Coenzyme F430 from Methanogenic Bacteria: Complete Assignment of Configuration Based on an X‐Ray Analysis of 12,13‐Diepi‐F430 Pentamethyl Ester and on NMR Spectroscopy

Abstract

The structure of a derivative of coenzyme F430 from methanogenic bacteria, the bromide salt of 12,13-diepi-F430 pentamethyl ester (5, X = Br), was determined by X-ray structure analysis. It reveals a more pronounced saddle-shaped out-of-plane deformation of the macrocycle than any hydroporphinoid Ni complex investigated so far. The crystal structure confirms the constitution proposed for coenzyme F430 (2) and shows that in the epimer 5, the three stereogenic centers in ring D, C(17), C(18), and C(19), have the (17s)-, (lXS)-, and (19R)-configuration, respectively. Deuteration and 2D-NMR studies independently demonstrate that native coenzyme F430 (2) has the same configuration in ring D as the epimer 5. Therefore, our original tentative assignment of configuration at C(19) and C(18) [l] has to be reversed. This completes the assignment of configuration for all stereogenic centers in coenzyme F430, which has the structure shown in Formula 2.1. Introduction. -In the previous papers in this series [1-4], we reported on the structure elucidation of coenzyme F430 [5] [6], a hydroporphinoid nickel complex which plays a central role in the energy metabolism of methanogenic bacteria [7]. As a component of methyl-coenzyme M reductase, it catalyzes the reductive cleavage of S-methylcoenzyme M to coenzyme M and methane [8] [9].Our structural studies which were carried out in close collaboration with the group of R . K. Thauer at the University of Marburg led to the structural formula 1 for coenzyme F430 (R = H). The constitution was determined largely by NMR analysis of the pentamethyl ester F430M in combination with a series of biosynthetic incorporation experiments using specifically I3C-labeled precursors [la] and UV/VIS studies of synthetic hydrocorphinoid model complexes [ 1 b]. Making extensive use of 1 D-NOE-difference spectroscopy, it was possible to establish the relative configuration at the six stereogenic centers in rings A and B and the trans-arrangement of the ring-C side chains, but not the configurational relationship between rings B and C. The absolute configuration at C( 12) and C( 13) was deduced by ozonolytic excision of ring C and CD-spectroscopic correlation of the resulting succinimide derivative with reference compounds of known absolute configuration [la]. The absolute configuration of the A/B fragment followed from comparison of the CD spectra of nickel(I1) isobacteriochlorinate derivatives prepared from F430 with the CD spectrum of nickel(I1) sirohydrochlorinate octamethyl ester [4].

Elucidating the Process of Activation of Methyl-Coenzyme M Reductase

“…For the methane production, it catalyzes the exergonic conversion of methyl coenzyme M (CH 3 MCR is composed of three different subunits, ␣, ␤, and ␥, forming an (␣␤␥) 2 heterohexamer (5). Each molecule of MCR contains two molecules of the cofactor F 430 , a Ni-porphinoid, as a prosthetic group (6)(7)(8). The binding sites of two coenzymes F 430 are roughly 50 Å apart, forming two separated structurally identical active sites.…”

Substrate‐analogue‐induced changes in the nickel‐EPR spectrum of active methyl‐coenzyme‐M reductase from Methanobacterium thermoautotrophicum

“…The results indicate that inhibition of MCR by the halogenated substrate analogues investigated above is not via oxidation of Ni(I)F430. The different MCR EPR signals are assigned to different enzyme/substrate and enzyme/inhibitor complexes.Methyl-coenzyme M reductase (MCR) is a nickel protein containing the nickel porphinoid coenzyme F430 as prosthetic group (DiMarco et al, 1990;Friedmann et al, 1990;Farber et al, 1991). The enzyme catalyzes the reduction of methylcoenzyme M (CH,-S-CoM) with 7-mercaptoheptanoylthreoCorrespondence to R. K.…”

“…Methyl-coenzyme M reductase (MCR) is a nickel protein containing the nickel porphinoid coenzyme F430 as prosthetic group (DiMarco et al, 1990;Friedmann et al, 1990;Farber et al, 1991). The enzyme catalyzes the reduction of methylcoenzyme M (CH,-S-CoM) with 7-mercaptoheptanoylthreoCorrespondence to R. K.…”

My Lifelong Passion for Biochemistry and Anaerobic Microorganisms

“…With this information, we asked Albert Eschenmoser at ETH Zürich whether he would help us unravel the structure of this novel compound. Together with Bernhard Jaun and Andreas Pfaltz, he solved the structure, mainly via NMR analysis of the biosynthetically, 13 C-differentially labeled pentamethyl ester (53,118).…”