HbYX Motifs
HbYX motif is a short, evolutionarily conserved peptide sequence found at the C‑termini of several proteasome activators. The "Hb" at the beginning of its name denotes a hydrophobic amino acid residue, "Y" indicates tyrosine, while "X" indicates a variable residue terminating with a free carboxylate group. Originally characterized in archaeal systems, the motif plays a central role in allosterically inducing gate opening of the 20S proteasome—thereby enabling regulated substrate entry and degradation. Recent studies in human and yeast proteasomes have revealed subtle differences in sequence preferences, prompting a re‐definition (in some contexts) of the motif as the “YΦ” motif, in which the penultimate tyrosine is strictly conserved and adjacent aromatic residues may be functionally interchangeable. Discovery The HbYX motif was identified from studies of archaeal Archaea ( ) is a domain of organisms. Traditionally, Archaea only included its prokaryotic members ...
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