@article{madding_michel_shockley_conners_epting_johnson_kelly_2007, title={Role of the beta 1 subunit in the function and stability of the 20S proteasome in the hyperthermophilic archaeon Pyrococcus furiosus}, volume={189}, ISSN={["0021-9193"]}, DOI={10.1128/JB.01382-06}, abstractNote={ABSTRACT The hyperthermophilic archaeon Pyrococcus furiosus genome encodes three proteasome component proteins: one α protein (PF1571) and two β proteins (β1-PF1404 and β2-PF0159), as well as an ATPase (PF0115), referred to as proteasome-activating nucleotidase. Transcriptional analysis of the P. furiosus dynamic heat shock response (shift from 90 to 105°C) showed that the β1 gene was up-regulated over twofold within 5 minutes, suggesting a specific role during thermal stress. Consistent with transcriptional data, two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that incorporation of the β1 protein relative to β2 into the 20S proteasome (core particle [CP]) increased with increasing temperature for both native and recombinant versions. For the recombinant enzyme, the β2/β1 ratio varied linearly with temperature from 3.8, when assembled at 80°C, to 0.9 at 105°C. The recombinant α+β1+β2 CP assembled at 105°C was more thermostable than either the α+β1+β2 version assembled at 90°C or the α+β2 version assembled at either 90°C or 105°C, based on melting temperature and the biocatalytic inactivation rate at 115°C. The recombinant CP assembled at 105°C was also found to have different catalytic rates and specificity for peptide hydrolysis, compared to the 90°C assembly (measured at 95°C). Combination of the α and β1 proteins neither yielded a large proteasome complex nor demonstrated any significant activity. These results indicate that the β1 subunit in the P. furiosus 20S proteasome plays a thermostabilizing role and influences biocatalytic properties, suggesting that β subunit composition is a factor in archaeal proteasome function during thermal stress, when polypeptide turnover is essential to cell survival.}, number={2}, journal={JOURNAL OF BACTERIOLOGY}, author={Madding, Lara S. and Michel, Joshua K. and Shockley, Keith R. and Conners, Shannon B. and Epting, Kevin L. and Johnson, Matthew R. and Kelly, Robert M.}, year={2007}, month={Jan}, pages={583–590} }