Peptidase_S41_N is a family found at the N-terminus of the functional unit of interphotoreceptor retinoid binding proteins 3, IRBP, in eukaryotes. From the structure of PDB:1j7x, the domain forms the N-terminal end of the module which is characterised as a serine-peptidase, Pfam:PF03572. Peptidase_S41_N forms a three-helix bundle followed by a small beta strand and is termed domain A. Part of the peptidase domain folds back over domain A to create a largely hydrophobic cleft between the two domains. On binding of ligand domain A is structurally rearranged with respect to domain B [1].

1: Crystal structure of the functional unit of interphotoreceptor retinoid binding protein. Loew A, Gonzalez-Fernandez F; Structure. 2002;10:43-49. PMID:11796109