MSP domain proteins.

The major sperm protein (MSP) has attracted interest because of its ability to mediate actin-like ameboid motility in nematode sperm, despite a lack of sequence or structural similarity to actin. The basic immunoglobulin-like organization of MSP defines a structural domain found in proteins from many eukaryotic species. Within the context of MSP domain proteins (MDPs), evidence suggests that this structure functions as a protein-protein interaction domain and a signaling element. In this article, we describe the current status of knowledge about the MDP family of proteins, outline their structure and phylogeny, and discuss potential roles of MDPs in the biology of parasitic nematodes.