K. Ferrell et al., MOLECULAR-CLONING AND EXPRESSION OF A MULTIUBIQUITIN CHAIN BINDING SUBUNIT OF THE HUMAN 26S PROTEASE, FEBS letters, 381(1-2), 1996, pp. 143-148
S5a is a subunit of the 26S protease that binds and presumably selects
multiubiquitinated proteins for destruction, We recently identified a
n Arabidopsis protein, MBP1, that is physically, inmunologically and b
iochemically similar to S5a from the human erythrocyte 26S protease. B
ased upon the MBP1 cDNA sequence we have now isolated a HeLa cell cDNA
coding for human S5a. The HeLa cDNA sequence is highly similar to MBP
1 and it encodes peptides obtained directly from human erythrocyte S5a
. Moreover, expression of the isolated cDNA in E. coli results in a re
combinant protein with an apparent molecular mass and multiubiquitin b
inding properties that match those of human S5a obtained from the puri
fied 26S enzyme.