Ternary complex

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A ternary complex is a protein complex containing three different molecules that are bound together. In structural biology, ternary complex can also be used to describe a crystal containing a protein with two small molecules bound, for example cofactor and substrate; or a complex formed between two proteins and a single substrate.[1] In Immunology, ternary complex can refer to the MHC–peptide–T-cell-receptor complex formed when T cells recognize epitopes of an antigen.

A ternary complex can be a complex formed between two substrate molecules and an enzyme. This is seen in multi-substrate enzyme-catalyzed reactions where two substrates and two products can be formed. The ternary complex is an intermediate between the product formation in this type of enzyme-catalyzed reactions. An example for a ternary complex is seen in random-order mechanism or a compulsory-order mechanism of enzyme catalysis for multi substrates.

The term ternary complex can also refer to a polymer formed by electrostatic interactions.[2]


  1. ^ Clarke, Steven G.; Tamanoi, Fuyuhiko (2006). Protein methyltransferases. Academic Press. pp. 162–172. ISBN 978-0-12-122725-8. 
  2. ^ Cabuil, Valérie; Levitz, Pierre; Treiner, Clande (2004). Trends in colloid and interface science XVII. Springer. p. 45. ISBN 978-3-540-20073-4. 

Trevor Palmer (Enzymes, 2nd edition)