This fibronectin type III domain is found in fungal chitin biosynthesis protein CHS5 where, together with the neighbouring BRCT domain (Pfam:PF00533), it binds to the Arf1 GTPase [1].

1: The exomer cargo adaptor structure reveals a novel GTPase-binding domain. Paczkowski JE, Richardson BC, Strassner AM, Fromme JC; EMBO J. 2012;31:4191-4203. PMID:23000721