Protein trimer

Assembled human PCNA (PDB 1AXC), a sliding DNA clamp protein that is part of the DNA replication complex and serves as a processivity factor for DNA polymerase. The three individual polypeptide chains that make up the trimer are shown.

In biochemistry, a trimer is a macromolecular complex formed by three, usually non-covalently bound, macromolecules like proteins or nucleic acids. A homo-trimer would be formed by three identical molecules. A hetero-trimer would be formed by three different macromolecules. Collagen is an example of homo-trimeric protein.

Porins usually arrange themselves in membranes as trimers.

See also

• Protein quaternary structure
• Oligomer