Ubiquitin-40S ribosomal protein S27a (Ubiquitin carboxyl extension protein 80) [Cleaved into: Ubiquitin; 40S ribosomal protein S27a (Small ribosomal subunit protein eS31)]
1_MQIFV 6_ KTLTG 11_ KTITL 16_ EVEPS 21_ DTIEN 26_ VKAKI 31_ QDKEG 36_ IPPDQ 41_ QRLIF 46_ AGKQL 51_ EDGRT 56_ LSDYN 61_ IQKES 66_ TLHLV 71_ LRLRG 76_ GAKKR 81_ KKKSY 86_ TTPKK 91_ NKHKR 96_ KKVKL 101_ AVLKY 106_ YKVDE 111_ NGKIS 116_ RLRRE 121_ CPSDE 126_ CGAGV 131_ FMASH 136_ FDRHY 141_ CGKCC 146_ LTYCF 151_NKPED
1: Exists either covalently attached to another protein, or free (unanchored). When covalently bound, it is conjugated to target proteins via an isopeptide bond either as a monomer (monoubiquitin), a polymer linked via different Lys residues of the ubiquitin (polyubiquitin chains) or a linear polymer linked via the initiator Met of the ubiquitin (linear polyubiquitin chains). Polyubiquitin chains, when attached to a target protein, have different functions depending on the Lys residue of the ubiquitin that is linked: Lys-6-linked may be involved in DNA repair; Lys-11-linked is involved in ERAD (endoplasmic reticulum-associated degradation) and in cell-cycle regulation; Lys-29-linked is involved in proteotoxic stress response and cell cycle; Lys-33-linked is involved in kinase modification; Lys-48-linked is involved in protein degradation via the proteasome; Lys-63-linked is involved in endocytosis, DNA-damage responses as well as in signaling processes leading to activation of the transcription factor NF-kappa-B. Linear polymer chains formed via attachment by the initiator Met lead to cell signaling. Ubiquitin is usually conjugated to Lys residues of target proteins, however, in rare cases, conjugation to Cys or Ser residues has been observed. When polyubiquitin is free (unanchored-polyubiquitin), it also has distinct roles, such as in activation of protein kinases, and in signaling
2: Component of the 40S subunit of the ribosome (PubMed:23636399, PubMed:9582194). Part of the small subunit (SSU) processome, first precursor of the small eukaryotic ribosomal subunit. During the assembly of the SSU processome in the nucleolus, many ribosome biogenesis factors, an RNA chaperone and ribosomal proteins associate with the nascent pre-rRNA and work in concert to generate RNA folding, modifications, rearrangements and cleavage as well as targeted degradation of pre-ribosomal RNA by the RNA exosome (PubMed:23636399, PubMed:34516797)