葉綠體是植物細胞進行光合作用重要的胞器。為了維持葉綠體的正常功能，從細胞核基因合成的葉綠體蛋白必須正確地被葉綠體膜上的轉運蛋白辨識及輸入。我們之前的研究顯示，CIA2蛋白是CCT-class的轉錄因子，可正向調控葉綠體運組基因Toc33和Toc75。本研究發現CIA2的CCT區域和HAP2序列具有相似性，且其保守胺基酸與HAP蛋白質交互作用及DNA結合有關。利用酵母菌雙雜交實驗證實CIA2和HAP5a、HAP5b及HAP5c有交互作用。檢測不同長度CIA2片段蛋白與HAP5進行酵母菌雙雜交實驗，結果顯示其N端序列和C端的CCT motif，可能與蛋白質交互作用有關。比對植物的CIA2同源蛋白發現N端序列和CCT motif皆具高度保守性，顯示CIA2的N端和CCT motif具有重要蛋白質功能。

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