page_title: Succinyl coenzyme A synthetase
section_title: Subunits
hierarchical_section_title: Succinyl coenzyme A synthetase / Structure / Subunits
context_page_description: Succinyl coenzyme A synthetase is an enzyme that catalyzes the reversible reaction of succinyl-CoA to succinate. The enzyme facilitates the coupling of this reaction to the formation of a nucleoside triphosphate molecule from an inorganic phosphate molecule and a nucleoside diphosphate molecule. It plays a key role as one of the catalysts involved in the citric acid cycle, a central pathway in cellular metabolism, and it is located within the mitochondrial matrix of a cell.
context_section_description: Bacterial and mammalian SCSs are made up of α and β subunits.  In E. coli two αβ heterodimers link together to form an α₂β₂ heterotetrameric structure.  However, mammalian mitochondrial SCSs are active as αβ dimers and do not form a heterotetramer.  
  The E. coli SCS heterotetramer has been crystallized and characterized in great detail.  As can be seen in Image 2, the two α subunits (pink and green) reside on opposite sides of the structure and the two β subunits (yellow and blue) interact in the middle region of the protein.  The two α subunits only interact with a single β unit, whereas the β units interact with a single α unit (to form the αβ dimer) and the β subunit of the other αβ dimer.  A short amino acid chain links the two β subunits which gives rise to the tetrameric structure.
  The crystal structure of Succinyl-CoA synthetase alpha subunit (succinyl-CoA-binding isoform) was determined by Joyce et al. to a resolution of 2.10 A, with PDB code 1CQJ.
caption: Image 2: The E. coli Succinyl-CoA Synthetase Heterotetramer; α subunits: pink and green, β subunits: yellow and blue. Pink and yellow form the one dimer and green and blue form the other dimer. PDB ID: 1CQG
exif: {}