The Spred family has the following domains: an N-terminal EVH1 domain, a unique KBD (c-Kit kinase binding) domain which that is phosphorylated by the stem cell factor receptor c-Kit, and a C-terminal cysteine-rich SPR (Sprouty-related) domain which is involved in membrane localization. There are 3 Spred proteins: Spred1 which interacts with both Ras and Raf through its SPR domain; Spred2 which is the most abundant isoform; and Spred3 which has a non-functional KBD and maintains the inhibitory action on Raf. Legius syndrome is caused by heterozygous mutations in Spred1. Both EVH1 and SPR domains are involved in the inhibition of the MAP kinase pathway by Spred proteins. The specific function of the Spred2 EVH1 domain is unknown and there are no known interacting proteins to date. It is thought that its EVH1 domain will have a fourth distinct peptide binding mechanism within the EVH1 family. The EVH1 domains are part of the PH domain superamily. There are 5 EVH1 subfamilies: Enables/VASP, Homer/Vesl, WASP, Dcp1, and Spred. Ligands are known for three of the EVH1 subfamilies, all of which bind proline-rich sequences: the Enabled/VASP family binds to FPPPP peptides, the Homer/Vesl family binds PPxxF peptides, and the WASP family binds LPPPEP peptides. EVH1 has a PH-like fold, despite having minimal sequence similarity to PH or PTB domains.
Jiyao W et al.(2023). "The conserved domain database in 2023.",