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異鈣調素結合在質膜胞外位點上并導致胞內鈣離子水平上升
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上圖:百合花粉CaM的定位以及原生質體質膜Ca2+流 鈣調蛋白(CaM)是一種高保守性的細胞內鈣離子感應器。在植物中,胞外CaM也作為一個多肽信號影響許多生理功能,但是其在細胞質外的結合位點至今仍存在爭議。 2009年5月,中科院植物所林金星研究組在《JBC》上發(fā)表文章,研究人員利用CaM交聯(lián)QD系統(tǒng)對植物細胞表面CaM結合位點進行單分子水平檢測,發(fā)現(xiàn)QD-CaM能選擇性的結合在質膜外空間,并且通過高分辨率透射電子顯微鏡進行了進一步定位,證實了胞外CaM結合位點確實存在于植物細胞膜表面,但在植物細胞壁上卻沒有CaM結合位點。此研究為鈉米技術在植物細胞研究上的應用提供了有力的證據(jù)。此外,研究人員還利用顯微注射、FRET以及非損傷微測(SIET)等技術證明了胞外CaM在與其胞外結合為點結合后,可以引起胞內第二信使Ca2+信號的增強,這些發(fā)現(xiàn)說明了植物胞外CaM可以通過介導跨膜信號而發(fā)揮其信號肽的功能。 相關鏈接:
http://xuyue.net/xylt/attachment.php?aid=164&noupdate=yes¬humb=yes http://xuyue.net/xylt/attachment.php?aid=165&noupdate=yes¬humb=yes http://www.ebiotrade.com/newsf/2009-3/2009325172825.htm 關鍵詞:鈣調素(Calmodulin, CaM);離子選擇性電極(Ion-selective microelectrodes);質膜(Plasma membrane)
參考文獻:Wang et al. J. Biol. Chem..2009, 284: 12000-12007
全文下載:http://dmdb.ibcas.ac.cn/ljx文章/JBC--wang%20qingli.pdf
Abstract
Calmodulin (CaM) is a highly conserved intracellular calcium sensor. In plants, CaM also appears to be present in the apoplasm, and application of exogenousCaMhas been shown to influence a number of physiological functions as a polypeptide signal; however, the existence and localization of its corresponding apoplasmic binding sites remain controversial. To identify the site(s) of action, a CaM-conjugated quantum dot (QD) system was employed for single molecule level detection at the surface of plant cells. Using this approach, we show that QD-CaM binds selectively to sites on the outer surface of the plasma membrane, which was further confirmed by high resolution transmission electron microscopy. Measurements of Ca2+ fluxes across the plasma membrane, using ion-selective microelectrodes, demonstrated that exogenous CaM induces a net influx into protoplasts. Consistent with these flux studies, calcium-green-dextran and FRET experiments confirmed that applied CaM/QD-CaM elicited an increase in cytoplasmic Ca2+ levels. These results support the hypothesis that apoplasmic CaMcan act as a signaling agent. These findings are discussed in terms of CaM acting as an apoplasmic peptide ligand to mediate transmembrane signaling in the plant kingdom. |