The eukaryotic LSm proteins (LSm2-8 or LSm1-7) assemble into a hetero-heptameric ring around the 3'-terminus uridylation tag of the gamma-methyl triphosphate (gamma-m-P3) capped U6 snRNA. LSm2-8 form the core of the snRNP particle that, in turn, assembles with other components onto the pre-mRNA to form the spliceosome which is responsible for the excision of introns and the ligation of exons. LSm1-7 is involved in recognition of the 3' uridylation tag and recruitment of the decapping machinery. LSm657 is believed to be an assembly intermediate for both the LSm1-7 and LSm2-8 rings. Members of this family share a highly conserved Sm fold containing an N-terminal helix followed by a strongly bent five-stranded antiparallel beta-sheet.
Comment:This oligomerization interface is flexible and plays a role in both the hexameric arrangement of assembly intermediates and the hetero-heptamer
Structure:3SWN, Schizosaccharomyces pombe LSm5-7 hetero-hexamer, contacts at 4A
Jiyao W et al.(2023). "The conserved domain database in 2023.",