Benaroudj Nadia, Zwickl Peter, Seemüller Erika, Baumeister Wolfgang, Goldberg Alfred L
Harvard Medical School, Department of Cell Biology, 240 Longwood Avenue, Boston, MA 02115, USA.
Mol Cell. 2003 Jan;11(1):69-78. doi: 10.1016/s1097-2765(02)00775-x.
To clarify the role of ATP in proteolysis, we studied archaeal 20S proteasomes and the PAN (proteasome-activating nucleotidase) regulatory complex, a homolog of the eukaryotic 19S ATPases. PAN's ATPase activity was stimulated similarly by globular (GFPssrA) and unfolded (casein) substrates, and by the ssrA recognition peptide. Denaturation of GFPssrA did not accelerate its degradation or eliminate the requirement for PAN and ATP. During degradation of one molecule of globular or unfolded substrates, 300-400 ATP molecules were hydrolyzed. An N-terminal deletion in the 20S alpha subunits caused opening of the substrate-entry channel and rapid degradation of unfolded proteins without PAN; however, degradation of globular GFPssrA still required PAN's ATPase activity, even after PAN-catalyzed unfolding. Thus, substrate binding activates ATP hydrolysis, which promotes three processes: substrate unfolding, gate opening in the 20S, and protein translocation.
为阐明ATP在蛋白质水解中的作用，我们研究了古细菌20S蛋白酶体和PAN（蛋白酶体激活核苷酸酶）调节复合物，它是真核生物19S ATP酶的同源物。球状（GFPssrA）和未折叠（酪蛋白）底物以及ssrA识别肽对PAN的ATP酶活性的刺激作用相似。GFPssrA的变性既没有加速其降解，也没有消除对PAN和ATP的需求。在降解一分子球状或未折叠底物的过程中，有300 - 400个ATP分子被水解。20S α亚基的N端缺失导致底物进入通道打开，并且在没有PAN的情况下未折叠蛋白快速降解；然而，即使经过PAN催化的解折叠，球状GFPssrA的降解仍然需要PAN的ATP酶活性。因此，底物结合激活ATP水解，这促进了三个过程：底物解折叠、20S中的门打开以及蛋白质转运。
