Tumour necrosis factor is a compact trimer.

Recombinant produced human tumour necrosis factor (TNF) has been studied to characterise the subunit structure of the protein. TNF is shown to be a trimer Mr 52000 in which the subunits are associated in a compact, triangular form. In secondary structure it belongs to the all-beta class of proteins. It has high thermodynamic stability and the unfolded subunits can fold and associate spontaneously to form native, biologically active TNF.