Article Abstract:
The importance of the beta-type proteasome subunit Doa3 is determined in 20S proteasome function in yeast. It is found that replacement of the leading Doa3 sequence is not possible with the propeptide of another beta subunit. A trans function by the Doa3 propeptide enables the insertion of the mature Doa3 domain into the proteasome. Such observation implies the role of Doa3 as a subunit-specific chaperone during proteasome biogenesis. Further results also suggest the importance of the N-terminal threonine of Doa3 in the chymotrysin-type active sites of proteasome.
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Article Abstract:
The gamma-interferon inducible PA28 protein complex, or 11S regulator, which is composed of two homologous subunit forming a hexa- or heptameric ring structure, is known to associate with the 20S proteasome particle. The kinetics of product generation by 20S proteasomes with and without PA28 is studied. Results indicate that the PA28 regulator significantly alters the cleavage mechanism of the proteasome and optimizes the generation of dominant T cell epitopes.
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Article Abstract:
Active site compartmentalization is another unique feature of cytoplasmic peptidases which features adenosine triphosphatase hydrolysis-assisted substrate unfolding. ATP hydrolysis directly provide the energy for translocation. Translocation in turn, commits the proteins to degradation resulting from hydrolysis of the substrate at the distal end of the selective channel.
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