The complementary DNA (PsU BC4) representing an mRNA encoding an ubiquitin-conjugating enzyme (UBC) of Pisum sativum has been cloned. The coding region is 444 nucleotides (nt) in length and capable of specifying a 16.5-kDa protein of 148 amino acids (aa) with an isoelectric point of 7.95. The deduced aa sequence showed 97% identity with Arabidopsis thaliana AtUBC8-12 families and tomato ERT17, and 80% identity with yeast ScUBC4 and ScUBC5 and Drosophila melanogaster DmUBC4. The active site cysteine (Cys85) found in UBCs so far described is also conserved in the P. sativum sequence.