[2] SAM domains have been shown to homo- and hetero-oligomerise, forming multiple self-association architectures and also binding to various non-SAM domain-containing proteins,[3] nevertheless with a low affinity constant.
[5] Smaug, a protein that helps to establish a morphogen gradient in Drosophila embryos by repressing the translation of nanos (nos) mRNA, binds to the 3' untranslated region (UTR) of nos mRNA via two similar hairpin structures.
This electropositive potential is unique among all previously determined SAM-domain structures and is conserved among Smaug-SAM homologs.
Structural analyses show that the SAM domain is arranged in a small five-helix bundle with two large interfaces.
The presence of these two distinct intermonomers binding surface suggest that SAM could form extended polymeric structures.