Proteinase yscE of yeast shows homology with the 20 S cylinder particles of Xenopus laevis

Abstract

Proteinase yscE of the yeast Saccharomyces cerevisiae has been compared with the 20 S cylinder particles of Xenopus laevis. Both proteins are characterized by a similar group of 10-12 polypeptides with molecular masses ranging between 21 and 38 kDa. Antibodies generated against the 20 S Xenopus cylinder particles show cross-reactivity with yeast proteinase yscE subunits. The Xenopus particles and yeast proteinase yscE exhibit an identical image in electron microscopy. Both proteins appear as hollow cylinders mostly composed of four stacked annuli. The Xenopus 20 S particles exhibit proteolytic activity against the three peptide derivatives known to be substrates of proteinase yscE. The pH optimum for activity and the inhibition spectrum of the proteolytic activities of Xenopus 20 S particles and of yeast proteinase yscE are identical. The RNA content of the cylinder particles and of proteinase yscE is below 0.1 RNA chain per molecule. Our data suggest that proteinase yscE from yeast and the 20 S cylinder particles of X. laevis are homologous, highly conserved proteins carrying the catalytic character of a peptidase.

The proteasome/multicatalytic—multifunctional proteinase In vivo function in the ubiquitin‐dependent N‐end rule pathway of protein degradation in eukaryotes

“…I A,B,C lanes I ,3,5,7), its content is considerabfy increased in all proteinasc yscE mutant cells ( Fig. 1 A,B,C lanes 2, 4,6,8), Here it reaches nearly the amount of bgal protein found for the most stable constructs in wild-type cells, Ser-&al and Ala-~gal (Fig. lA,B,C Ianes 9 and 11).…”

Co‐purification of a small RNA species with multicatalytic proteinase (proteasome) from rat liver

“…The ratio of absorbance at 280 nm to that at 260 nm was 1.8, 2.0 and 1.5 for A, B and C, respectively. It was concluded from previously reported A2so:A260 values of 1.94 and 1.6 that the RNA content of MCP must be less than 0.1% of particle mass [14,15].…”

“…Although it is generally agreed that prosomes contain RNA [3, 8-I I] there is disagreement concerning the existence of RNA in MCP [12] and other cylindrical particles [13][14][15]. These contradictory observations may possibly have arisen from the use of very different protein purification procedures, and, in some cases, by the use of insensitive RNA detection methods.…”

Differential proteolytic sensitivity of yeast fatty acid synthetase subunits α and β contributing to a balanced ratio of both fatty acid synthetase components

“…Because proteinases yscA and yscB together are responsible for about 85% of the yeast proteolytic activity under non-fermentative conditions [38] and since yscA and/or yscB are required for the activation of the zymogen forms of most known vacuolar hydrolases [ll], these findings are most easily explained by assuming a cytosolic proteinase being induced under less favourable nutritional conditions. A possible candidate might be the non-vacuolar proteinase yscE, the yeast equivalent to the high-molecular mass proteasome found in mammalian tissues [43]. However, proteinase yscE activity is not significantly regulated during the different growth phases of yeast [44], as is observed for the degradation of free FAS subunit a.…”