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The ubiquitin‐like protein HUB1 forms SDS‐resistant complexes with cellular proteins in the absence of ATP
Author(s) -
Lüders Jens,
Pyrowolakis George,
Jentsch Stefan
Publication year - 2003
Publication title -
embo reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.584
H-Index - 184
eISSN - 1469-3178
pISSN - 1469-221X
DOI - 10.1038/sj.embor.7400025
Subject(s) - ubiquitin , biochemistry , lysine , peptide sequence , covalent bond , sumo enzymes , amino acid , residue (chemistry) , chemistry , biology , ubiquitin ligase , gene , organic chemistry
Ubiquitin and ubiquitin‐like modifiers (UBLs) form covalent complexes with other proteins by isopeptide formation between their carboxyl (C)‐termini and ε‐amino groups of lysine residues of acceptor proteins. A hallmark of UBLs is a protruding C‐terminal tail with a terminal glycine residue, which is required for ATP‐dependent conjugation. Recently, the highly conserved protein HUB1 (homologous to ubiquitin 1) has been reported to function as a UBL following C‐terminal processing. HUB1 exhibits sequence similarity with ubiquitin but lacks a C‐terminal tail bearing a glycine residue. Here we show that HUB1 can form SDS‐resistant complexes with cellular proteins, but provide evidence that these adducts are not formed through covalent C‐terminal conjugation of HUB1 to substrates. The adducts are still formed when the C‐terminus of HUB1 was altered by epitope tagging, amino‐acid exchange or deletion, or when cells were depleted of ATP. We propose that HUB1 may act as a novel protein modulator through the formation of tight, possibly noncovalent interactions with target proteins.