The sterile α motif (SAM) domain is a putative protein interaction module present in a wide variety of proteins [1] involved in many biological processes. The SAM domain that spreads over around 70 residues is found in diverse eukaryotic organisms [2]. SAM domains have been shown to homo- and hetero-oligomerize [3], nevertheless with a low-affinity constant [4], and to mediate specific protein-protein interactions.

Structural analyses show that the SAM domain is arranged in a small five-helix bundle with two large interfaces [3,4]. In the case of the SAM domain of EphB2, each of these interfaces is able to form dimers [4]. The presence of these two distinct intermonomers binding surface suggest that SAM could form extended polymeric structures [4].

Some of the proteins in which such a domain is known to exist are listed below.

• Vertebrate Eph receptor protein tyrosine kinases. Involved in developmental regulation.
• Yeast STE11, serine/threonine protein kinase which participates in mating pheromone response pathways.
• Mammalian liprin α. Interacts with LAR transmembrane protein tyrosine phosphatase.
• Mammalian Neurabin actin filament binding protein. Involved in neurite formation.
• Mammalian inositol phosphatase protein Ship2.
• Mammalian SH2 domain-containing leukocyte Protein of 76kDa (SLP-76). Hematopoietic cell specific molecule, critical for T cell development.
• Mammalian ETS translocation variant (ETV) or TEL. Translocations which fuse the SAM domain from ETV to Abl, PDGFB, JAK2 or AML1 have been associated with many human leukemias.
• Drosophila polyhomeotic (ph) and Sex comb on midleg (Scm), member of the Polycomb group genes, implied in the transcriptional repression of homeotic genes.
• Mammalian Polycomb group proteins Rae-28/MPH1 and SCML1. Homologues of drosophila ph and Scm proteins.

We developed a profile that spans the whole domain.