SAM (sterile alpha motif) domain of VTS1 subfamily proteins is RNA binding domain located in the C-terminal region. SAM interacts with stem-loop structures of mRNA. Proteins of this subfamily participate in regulation of transcript stability and degradation, and also may be involved in vacuolar protein transport regulation. VTS1 protein of S.cerevisiae induces mRNA degradation via the major deadenylation-dependent mRNA decay pathway; VTS1 recruits CCR4/POP2/NOT deadenylase complex to target mRNA. The recruitment is the initial step resulting in poly(A) tail removal transcripts. Potentially SAM domain may be responsible not only for RNA binding but also for deadenylase binding.
Comment:Specificity of RNA binding relies on a shallow pocket of the SAM domain interactions with a guanosine loop base and on the SAM domain contacts to the unique backbone structure of the loop. (RNA binding site is combined from two structure evidences).
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