Open AccessStructural insights into the inhibition properties of archaeon citrate synthase from Metallosphaera sedula
Author(s) -
Seul Hoo Lee,
Hyeoncheol Francis Son,
Kyungjin Kim
Publication year - 2019
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0212807
Subject(s) - citrate synthase , biochemistry , glyoxylate cycle , chemistry , cofactor , non competitive inhibition , enzyme , citric acid cycle , active site , stereochemistry , enzyme kinetics , nad+ kinase
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 ( Ms CS) 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 Ms CS, we determined its crystal structure at 1.7 Å resolution. Like other Type-I CS, Ms CS 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, Ms CS is non-competitively inhibited by NADH. Finally, amino acids and structural comparison of Ms CS with other Type-II CSs, which were reported to be non-competitively inhibited by NADH, revealed that Ms CS has quite unique NADH binding mode for non-competitive inhibition.