Structural insights into the inhibition properties of archaeon citrate synthase from Metallosphaera sedula

PLoS One. 2019 Feb 22;14(2):e0212807. doi: 10.1371/journal.pone.0212807. eCollection 2019.

Abstract

Metallosphaera sedula is a thermoacidophilic archaeon and has an incomplete TCA/glyoxylate cycle that is used for production of biosynthetic precursors of essential metabolites. Citrate synthase from M. sedula (MsCS) is an enzyme involved in the first step of the incomplete TCA/glyoxylate cycle by converting oxaloacetate and acetyl-CoA into citrate and coenzyme A. To elucidate the inhibition properties of MsCS, we determined its crystal structure at 1.7 Å resolution. Like other Type-I CS, MsCS functions as a dimer and each monomer consists of two distinct domains, a large domain and a small domain. The oxaloacetate binding site locates at the cleft between the two domains, and the active site was more closed upon binding of the oxaloacetate substrate than binding of the citrate product. Interestingly, the inhibition kinetic analysis showed that, unlike other Type-I CSs, MsCS is non-competitively inhibited by NADH. Finally, amino acids and structural comparison of MsCS with other Type-II CSs, which were reported to be non-competitively inhibited by NADH, revealed that MsCS has quite unique NADH binding mode for non-competitive inhibition.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Archaeal Proteins* / antagonists & inhibitors
  • Archaeal Proteins* / chemistry
  • Binding Sites
  • Citrate (si)-Synthase* / antagonists & inhibitors
  • Citrate (si)-Synthase* / chemistry
  • Crystallography, X-Ray
  • Enzyme Inhibitors / chemistry*
  • Protein Multimerization*
  • Protein Structure, Quaternary
  • Substrate Specificity
  • Sulfolobaceae / enzymology*

Substances

  • Archaeal Proteins
  • Enzyme Inhibitors
  • Citrate (si)-Synthase

Grants and funding

This work was supported by the C1 Gas Refinery Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (NRF-2016M3D3A1A01913269), and also supported by a National Research Foundation of Korea (NRF) grant (NRF-2014M1A2A2033626). H-F Son was supported by the NRF-2015-Global PhD Fellowship Program of the Korean Government (2015H1A2A1034233). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.