cDNA clone MS73 codes for an ATPase that is a regulatory subunit of the 26 S proteasome. Reverse transcriptase polymerase chain reaction analysis demonstrates that the expression of the gene dramatically increases in the pre-eclosion period. Western analyses show increases in other related. ATPases including MS73, MSS1, and mts2 but not TBP1. A similar increase in the 30-kDa subunit of the 20 S proteasome occurs. There are accompanying large changes in the peptidase activities of the 26 S proteasome. Relative to the 30-kDa subunit, there is no change in MSS1 and MS73, a 3-fold increase in mts2, and a 5-fold decline in TBP1. A large increase in the concentration of 26 S proteasomes together with extensive regulatory reprogramming may facilitate rapid muscular proteolysis.
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