Identification, Purification, and Characterization of a PA700-dependent Activator of the Proteasome

摘要: The activity of the intracellular protease, proteasome, is modulated by a number specific regulatory proteins. One such regulator, PA700, 700,000-Da multisubunit protein that activates hydrolytic activities proteasome via mechanism involves ATP-dependent formation proteasome-PA700 complex. Four subunits PA700 have been shown previously to be members family contains consensus sequence for ATP binding, and purified expresses ATPase activity. We report here identification, purification, initial characterization new modulator proteasome. has no direct effect on but enhances activation up 8-fold. This associated with proteasome/PA700-containing complex significantly larger than formed in its absence. native Mr ∼300,000, as determined gel filtration chromatography, composed three electrophoretically distinct values 50,000, 42,000, 27,000 (p50, p42, p27, respectively). Amino acid analysis shows p50 p42 are same ATP-binding found PA700. subunit identical TBP1, reported interact human immunodeficiency virus Tat (Nelbock, P., Dillion, P. J., Perkins, A., Rosen, C. A.(1990) Science 248, 1650-1653), while seems member family. p27 significant similarity any described protein. Both not were also identified components increasing this six. Thus, common two complexes regulate PA700-dependent activator represents growing list proteins