Protein-Protein Interaction of Starch Phosphorylase from Sweet Potato roots.
| Autor: | I-Min Chou, 周宜旻 |
|---|---|
| Rok vydání: | 2005 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 93 Proteasome is a controlled proteolytic system in eukaryotic cell, which degrades proteins recognizied and modified by ubiquitins. This ubiquitin-proteasome system plays important physiological roles, and might regulate the activity of proteins or enzymes in the cell. On the molecule of L-form starch phosphorylase (L-SP), several PEST regions and destruction boxes were found, indicating that it was subjected to degradation. Chen et al. (2002) showed that this proteolytic modification might play a regulatory role in controlling the direction of the L-SP catalysis. On the native electrophoresis gel for L-SP activity during the purification of L-SP, Chang et al. (1999) have found a high-molecular-weight band (HX) showing L-SP activity, which contains both proteasome and L-SP. Chen (2001) further analyzed the composition of HX by the affinity absorbent using specific antibodies against proteasome or L-SP, which was also confirmed by Lin (2003) using double diffusion. This study further improved the purification procedure for HX by tracing the overlaping activity fractions for L-SP and proteasome. The binding of J3b antibody to its epitope on L-SP was blocked by proteasome, as observed by native-PAGE immunoblotting. However, this blocking of antibody binding was relieved on SDS-PAGE immunoblot indicating that L-SP might be bound to proteasome in its N-terminal half. The HX protein was further analyzed by Blue native-PAGE and LC/MS/MS to reveal its components as L-SP and proteasome. The ubiquitin- and proteasome-dependent proteolytic pathway might take phosphorylated protein as one of its targets. However, we have only detected very small amount of phosphorylated L-SP in sweet potato roots. Further study is needed to elucidate the physiological function of the phsophorylation of L-SP and its association with the ubiquitin-proteasome system. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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