Structural basis for the binding of succinate to succinyl-CoA synthetase

2016 ◽  
Vol 72 (8) ◽  
pp. 912-921 ◽  
Author(s):  
Ji Huang ◽  
Marie E. Fraser

Succinyl-CoA synthetase catalyzes the only step in the citric acid cycle that provides substrate-level phosphorylation. Although the binding sites for the substrates CoA, phosphate, and the nucleotides ADP and ATP or GDP and GTP have been identified, the binding site for succinate has not. To determine this binding site, pig GTP-specific succinyl-CoA synthetase was crystallized in the presence of succinate, magnesium ions and CoA, and the structure of the complex was determined by X-ray crystallography to 2.2 Å resolution. Succinate binds in the carboxy-terminal domain of the β-subunit. The succinate-binding site is near both the active-site histidine residue that is phosphorylated in the reaction and the free thiol of CoA. The carboxy-terminal domain rearranges when succinate binds, burying this active site. However, succinate is not in position for transfer of the phosphoryl group from phosphohistidine. Here, it is proposed that when the active-site histidine residue has been phosphorylated by GTP, the phosphohistidine displaces phosphate and triggers the movement of the carboxylate of succinate into position to be phosphorylated. The structure shows why succinyl-CoA synthetase is specific for succinate and does not react appreciably with citrate nor with the other C4-dicarboxylic acids of the citric acid cycle, fumarate and oxaloacetate, but shows some activity with L-malate.

2021 ◽  
Vol 77 (3) ◽  
pp. 357-368
Author(s):  
Ji Huang ◽  
Marie E. Fraser

Succinyl-CoA synthetase (SCS) catalyzes a reversible reaction that is the only substrate-level phosphorylation in the citric acid cycle. One of the essential steps for the transfer of the phosphoryl group involves the movement of the phosphohistidine loop between active site I, where CoA, succinate and phosphate bind, and active site II, where the nucleotide binds. Here, the first crystal structure of SCS revealing the conformation of the phosphohistidine loop in site II of the porcine GTP-specific enzyme is presented. The phosphoryl transfer bridges a distance of 29 Å between the binding sites for phosphohistidine in site I and site II, so these crystal structures support the proposed mechanism of catalysis by SCS. In addition, a second succinate-binding site was discovered at the interface between the α- and β-subunits of SCS, and another magnesium ion was found that interacts with the side chains of Glu141β and Glu204β via water-mediated interactions. These glutamate residues interact with the active-site histidine residue when it is bound in site II.


2004 ◽  
Vol 15 (9) ◽  
pp. 3986-3993 ◽  
Author(s):  
Erik Vassella ◽  
Matthias Probst ◽  
André Schneider ◽  
Erwin Studer ◽  
Christina Kunz Renggli ◽  
...  

In cycling between the mammalian host and the tsetse fly vector, trypanosomes undergo major changes in energy metabolism and surface coat composition. Early procyclic (insect) forms in the tsetse fly midgut are coated by glycoproteins known as EP and GPEET procyclins. EP expression continues in late procyclic forms, whereas GPEET is down-regulated. In culture, expression of GPEET is modulated by glycerol or glucose. Here, we demonstrate that a glycerol-responsive element of 25 nucleotides within the 3′ untranslated region of GPEET mRNA also controls expression by glucose and during development in the fly. In trypanosomes, mitochondrial ATP is produced mainly by the acetate: succinate-CoA transferase/succinyl-CoA synthetase (ASCT) cycle, the citric acid cycle, and the cytochromes. Silencing of the pyruvate dehydrogenase or succinyl-CoA synthetase from the ASCT cycle by RNA interference induces reexpression of GPEET in late procyclic forms, whereas inhibition of the citric acid cycle or the cytochromes has no effect. In contrast, inhibition of the alternative oxidase, the second branch of the electron transport chain, with salicylhydroxamic acid overrides the effect of glucose or glycerol and causes a reduction in the level of GPEET mRNA. Our results reveal a new mechanism by which expression of a surface glycoprotein is controlled by the activity of mitochondrial enzymes.


1963 ◽  
Vol 42 (4) ◽  
pp. 480-484 ◽  
Author(s):  
B. Eckstein ◽  
R. Landsberg

ABSTRACT The succinic, malic and isocitric dehydrogenases in the ovary of immature and mature, normal and serum gonadotrophin injected rats were examined. The Qo2 of these enzymes were markedly enhanced in the gonadotrophin injected rats of both age groups, except in the case of succinic dehydrogenase in the ovary of the immature rats, where a slight non-significant decrease was noted. It is concluded that in the mature rat ovary, gonadotrophin administration stimulates the activity of all the examined dehydrogenases of the citric acid cycle, whereas in the immature rat ovary, at least the isocitric- and malic dehydrogenases are thus stimulated.


1951 ◽  
Vol 193 (1) ◽  
pp. 277-283 ◽  
Author(s):  
CharlesE. Frohman ◽  
JamesM. Orten ◽  
ArthurH. Smith

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