|Budget Amount *help
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2004: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2003: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2002: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2001: ¥1,300,000 (Direct Cost: ¥1,300,000)
Proteasome is a most important protease particle composed of 28 hetero-subunits. It functions a proteolysis in the cell to maintain stable it, and has the molecular weight of 750kDa, a large multifunctional enzyme. Proteasomes are also having an immuno-response by generating antigenic peptides presented by class I molecules of major histocompatibility complex when the proteasome activator (PA28) binds proteasomes. In this work, a structural investigation of the 20S proteasome from bovine liver and the proteolytic mechanism inside β-subunits are discussed.
20S proteasomes are isolated and purified from bovine liver, and crystallized (Y.Morimoto, et al., J.B., 1995). It has good quality for a structure analysis (Y.Tomisugi, et al., J.B., 2000). A structural refinement (M.Unno, et.al., Structure, 2002) with non-crystallographic symmetry operations goes down the crystallographic R-factor to 25.0% (FreeR=29.4%). One of features for a crystal structure of proteasomes is a location of acidic amino acids of the central cavity in proteasomes. It seems likely to present the mechanism of strict proteolysis against unneeded protein or antigen-presenting. Constitutive 20S proteasomes have three active subunits, β1, β2 and β5, which are replaced in the immunoproteasome by interferon-γ-inducible subunits β1i, β2i and β5i, respectively. A catalytic activity is discussed that in the β7 subunit N104, T1, D59 and R99 hold peptide chain by helping of Y88 in β1 subunit. The reaction is completed when the α-amino group donates a proton to the nucleophile.