| Summary: | 碩士 === 中國文化大學 === 生物科技研究所 === 89 === A circadian oscillating protein of 23 kDa (COP23) located in the cell membrane of unicellular cyanobacterium Synechococcus RF-1 exhibits a diurnal rhythm after 12h L/12h D entrainment. The content of COP23 declined to nearly undetectable level at light phase and reached a peak during dark phase. If L/D-entrained culture of Synechococcus RF-1 was transferred to continuous darkness, the degradation of COP23 was prevented. However, if the dark culture was illuminated at the suggestive light phase, COP23 degradation resumed. Thus, light is essential for COP23 degradation. Comparing the different kind of light on COP23 degradation, including blue, white, and red light, blue light showed the most efficiency. In addition, modification of COP23 was detected if the extracted membrane proteins were illuminated in vitro. After SDS-PAGE analysis, the modified band of COP23 revealed slower migration rate than unmodified form. The results showed that the modification is specific for COP23, and the degree of modification is dependent on light strength and duration of illumination.In addition, the COP23 modification was inhibited by sodium azide (NaN3) , however, the inhibitory mechanism was unclear.
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