碩士 / 國立臺灣大學 / 生化科學研究所 / 90 / Ω-Crystallin is a taxon-specific crystallin. It is present as a major protein in lenses of invertebrates, such as octopus, squid, and scallop, etc. Ω-Crystallin is similar to aldehyde dehydrogenase in protein sequence, yet possessing no enzyme activity. In this study, we use octopus Ω-crystallin to investigate its biophysical and biochemical properties, such as thermostability, polymerization, and enzyme activity. Gel filtration and ultracentrifugation studies indicated that octopus Ω-crystallin is a tetrameric protein. Circular dichroism analysis showed that the secondary structure of octopus Ω-crystallin is predominantly a-helical structure. Octopus Ω-crystallin was shown to behave similar to aldehyde dehyderogenase in thermostability and urea denaturation studies. However, it is unstable under UV irradiaton. By aldehyde dehydrogenase activity assay, octopus Ω-crystallin was found to be devoid of dehydrogenase activity. By isothermal microcalorimetry, octopus W-crystallin was found to bind b-NAD tightly. The lack of enzyme activity for Ω-crystallin was probably due to cysteine -> arginine mutantion at the active site as revealed by structural comparison based on computer homology modeling. Octopus W-crystallin was also found to possess no chaperone-like activity in contrast to a-crystallins present in most vertebrate species.
| Identifer | oai:union.ndltd.org:TW/090NTU00103014 |
| Date | January 2002 |
| Creators | CHUN-JEN, LIN, 林峻任 |
| Contributors | Shyh-Horng, Chiou, 邱式鴻 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 100 |
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