Identification and characterization of a bacterial core methionine synthase

Abstract: Methionine synthases are essential enzymes for amino acid and methyl group metabolism in all domains of life. Here, we describe a putatively anciently derived type of methionine synthase yet unknown in bacteria, here referred to as core-MetE. The enzyme appears to represent a minimal MetE form and transfers methyl groups from methylcobalamin instead of methyl-tetrahydrofolate to homocysteine. Accordingly, it does not possess the tetrahydrofolate binding domain described for canonical bacterial MetE proteins. In Dehalococcoides mccartyi strain CBDB1, an obligate anaerobic, mesophilic, slowly growing organohalide-respiring bacterium, it is encoded by the locus cbdbA481. In line with the observation to not accept methyl groups from methyl-tetrahydrofolate, all known genomes of bacteria of the class Dehalococcoidia lack metF encoding for methylene-tetrahydrofolate reductase synthesizing methyl-tetrahydrofolate, but all contain a core-metE gene. We heterologously expressed core-MetECBDB in E. coli and purified the 38 kDa protein. Core-MetECBDB exhibited Michaelis-Menten kinetics with respect to methylcob(III)alamin (KM ≈ 240 µM) and L-homocysteine (KM ≈ 50 µM). Only methylcob(III)alamin was found to be active as methyl donor with a kcat ≈ 60 s−1. Core-MetECBDB did not functionally complement metE-deficient E. coli strain DH5α (ΔmetE::kan) suggesting that core-MetECBDB and the canonical MetE enzyme from E. coli have different enzymatic specificities also in vivo. Core-MetE appears to be similar to a MetE-ancestor evolved before LUCA (last universal common ancestor) using methylated cobalamins as methyl donor whereas the canonical MetE consists of a tandem repeat and might have evolved by duplication of the core-MetE and diversification of the N-terminal part to a tetrahydrofolate-binding domain

Object Details

• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch
• Notes: Scientific reports. - 10 (2020) , 2100, ISSN: 2045-2322

Classification and Topics

• Classification: Chemie

Contributors, Places and Time

• Event: Veröffentlichung
• (where): Freiburg
• (who): Universität
• (when): 2023
• Creator: Deobald, Darja ; Hanna, Rafael ; Shahryari, Shahab ; Layer, Gunhild ; Adrian, Lorenz
• Contributor: Lehrstuhl der Pharmazeutischen Biologie & Biotechnologie, AG Prof. Dr. G. Layer

Further information

• DOI: 10.1038/s41598-020-58873-z
• URN: urn:nbn:de:bsz:25-freidok-2357269
• Rights: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Last update: 25.03.2025, 1:47 PM CET