Function:Protein modifier which can be covalently attached to target lysines either as a monomer or as a lysine-linked polymer. Attachment to proteins as a Lys-48-linked polymer usually leads to their degradation by proteasome. Attachment to proteins as a monomer or as an alternatively linked polymer does not lead to proteasomal degradation and may be required for numerous functions , including maintenance of chromatin structure , regulation of gene expression , stress response , ribosome biogenesis and DNA repair. ,miscellaneous:This ribosomal protein is synthesized as a C-terminal extension protein (CEP) of ubiquitin. ,miscellaneous:Ubiquitin is synthesized as a polyubiquitin precursor with exact head to tail repeats , the number of repeats differ between species and strains. In some species there is a final amino-acid after the last repeat , here in human a Val. Some ubiquitin genes contain a single copy of ubiquitin fused to a ribosomal protein (either L40 or S27a) . ,PTM:Several types of polymeric chains can be formed , depending on the lysine used for the assembly. ,similarity:Belongs to the ribosomal protein L40e family. ,similarity:Belongs to the ribosomal protein S27Ae family. ,similarity:Belongs to the ubiquitin family. ,
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