LSm
（重定向自Smith antigen）
![The LSm protein Hfq hexamer torus showing the peptide backbone, with each protein in a different color, representing each beta strand as a ribbon, each alpha helix as a cylinder and the RNA oligonucleotide as a 300° arc.](/Images/godic/202502/11/LSm_1I5L_10004.JPG")
![](/Images/godic/202502/11/PDB_1h64_EBI0004.jpg")
![LSm secondary structure showing the N-terminal alpha helix and the five-strand antiparallel beta sheet.](/Images/godic/202502/11/LSm_Secondary_Structure0004.JPG")
![The LSm protein Human SmD1 showing the eight-strand beta sandwich peptide backbone description. (The beta sheet fold hinge runs along the bottom of the image.)](/Images/godic/202502/11/1B34_SmD1_8strand0004.JPG")
In molecular biology, LSm proteins are a family of RNA-binding proteins found in virtually every cellular organism. LSm is a contraction of 'like Sm', because the first identified members of the LSm protein family were the Sm proteins. LSm proteins are defined by a characteristic three-dimensional structure and their assembly into rings of six or seven individual LSm protein molecules, and play a large number of various roles in mRNA processing and regulation.