This is a longin domain which is found in the N-terminal region of Lst4 proteins in yeast. Lst4 is the Fnip1/2 orthologue found in mammals. Lst4 forms a complex with Lst7 and are targeted to the vacuole when the cells are starved of carbon, and to a lesser extent nitrogen. Lst4 and Fnip1/2 belong to the DENN family of proteins which comprise an N-terminal longin domain, commonly found in a variety of trafficking proteins, and a C-terminal DENN domain. This domain is made up of a core five-strand beta-sheet, with one short alpha-helix [1].

1: Lst4, the yeast Fnip1/2 orthologue, is a DENN-family protein. Pacitto A, Ascher DB, Wong LH, Blaszczyk BK, Nookala RK, Zhang N, Dokudovskaya S, Levine TP, Blundell TL; Open Biol. 2015;5:150174. PMID:26631379