This domain is predominantly found in the structural protein coronin, and is duplicated in some sequences. It appears to have the function of stabilising the topology of short coiled-coils in proteins [1].

1: A conserved trimerization motif controls the topology of short coiled coils. Kammerer RA, Kostrewa D, Progias P, Honnappa S, Avila D, Lustig A, Winkler FK, Pieters J, Steinmetz MO; Proc Natl Acad Sci U S A. 2005;102:13891-13896. PMID:16172398