This domain is found in Tyrosine-protein kinase receptor torso from Bombyx mori (Tor), which is involved in the initiation of metamorphosis during postembryonic development. This protein is organised into two unusual domains with a fibronectin type III (FN3) fold, an N-terminal (this entry) and a C-terminal (Pfam:PF07714). This domain has an N-terminal alpha-helical extension [1].

1: Structural Basis of Neurohormone Perception by the Receptor Tyrosine Kinase Torso. Jenni S, Goyal Y, von Grotthuss M, Shvartsman SY, Klein DE; Mol Cell. 2015;60:941-952. PMID:26698662