Bacteria at Work – Experimental and Theoretical Studies Reveal the Catalytic Mechanism of Ectoine Synthase

• Published in: Chemistry : a European journal Vol. 30; no. 23; pp. e202304163 - n/a
• Main Authors: Andrys‐Olek, Justyna, Kluza, Anna, Tataruch, Mateusz, Heider, Johann, Korecki, Józef, Borowski, Tomasz
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 22.04.2024
• Subjects: Amino acids; Bacteria; Biosynthesis; Coordination numbers; Ectoine; ectoine synthase; Eukaryotes; Ferrous ions; Iron; metalloenzyme; Molecular dynamics; Mossbauer spectroscopy; Mössbauer spectroscopy; QM/MM; Reaction mechanism; ectoine synthase; Mössbauer spectroscopy; Reaction mechanism; iron; QM/MM; ectoine; metalloenzyme
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.202304163

Ectoine synthase (EctC) catalyses the ultimate step of ectoine biosynthesis, a kosmotropic compound produced as compatible solute by many bacteria and some archaea or eukaryotes. EctC is an Fe2+‐dependent homodimeric cytoplasmic protein. Using Mössbauer spectroscopy, molecular dynamics simulations and QM/MM calculations, we determined the most likely coordination number and geometry of the Fe2+ ion and proposed a mechanism of the EctC‐catalysed reaction. Most notably, we show that apart from the three amino acids binding to the iron ion (Glu57, Tyr84 and His92), one water molecule and one hydroxide ion are required as additional ligands for the reaction to occur. They fill the first coordination sphere of the Fe2+‐cofactor and act as critical proton donors and acceptors during the cyclization reaction. Ectoine is a compound gaining popularity in recent years, having unique moisturizing and cell‐protective properties. This osmolyte is produced by many bacteria species via the ectoine biosynthetic pathway, the final stage of which is catalyzed by Ectoine Synthase (EctC). Here, the catalytic mechanism of EctC is proposed, supported by theoretical (QM/MM) and experimental studies (Mossbauer spectroscopy).