PRTl of Arabidopsis thaliana encodes a component of the plant N-end rule pathway

Mutants in the PRT1 gene of Arabidopsis thaliana are impaired in the degradation of a normally short-lived intracellular protein that contains a destabilizing N-terminal residue, Proteins bearing such residues are the substrates of an ubiquitin-dependent proteolytic system called the N-end rule pathway, The chromosomal position of PRT1 was determined, and the PRT1 gene was isolated by map-based cloning, The 45-kDa PRT1 protein contains two RING finger domains and one ZZ domain, No other proteins in databases match these characteristics of PRT1, There is, however, a weak similarity to Rad18p of Saccharomyces cerevisiae, The RING finger domains have been found in a number of other proteins that are involved in ubiquitin conjugation, consistent with the proposed role of PRT1 in the plant N-end rule pathway.