Despite the critical importance of protein ubiquitination in the regulation of diverse cellular processes, the molecular mechanisms by which cells rec-ognize and transmit ubiquitin signals remain poorly understood. The endosomal sorting machinery component hepatocyte growth factor-regu-lated tyrosine kinase substrate (Hrs) contains a ubiquitin-interacting motif (UIM), which is believed to bind ubiquitinated membrane cargo proteins and mediate their sorting to the lysosomal degradation pathway.
