Saposin-like proteins (SAPLIP) carry out diverse functions on a common backbone structure.

Abstract

A polypeptide motif characterized by the locations of six cysteines and several hydrophobic residues is found in saposins A-D, sulfated glycoprotein-1, acid sphingomyelinase (ASM), acyloxyacyl hydrolase (AOAH), surfactant protein B (SPB), and Entamoeba hktolytku poreforming peptides (amoebapores) (1-4).The same motif is present, in an altered form, in plant aspartyl proteases (5).Each of the animal proteins binds to, or interacts with, one or more lipids, yet their properties and presumed functions in vivo are otherwise quite varied.In this article we review information about the members of this family and propose, as suggested in part by others (4), that three intradomain disulfide linkages create a common structural framework upon which amino acids in four amphipathic alpha helices can carry out diverse functions.The amino acid sequences of the saposin-like domains are compared in Fig. 1. Known members of the SAPosin-LUce Protein (SAPLIP) family