DEAD box為一蛋白質家族的通稱,在原核生物真核生物細胞中皆有,因其中一個結構域有一天門冬胺酸-麩胺酸-丙胺酸-天門冬胺酸(DEAD)的氨基酸序列而得名[2]。此家族的蛋白多參與RNA相關反應[3],有許多蛋白為RNA解旋酶[4],可以消耗ATP的機制將雙股RNA解開[5]

DEAD/DEAH box RNA解旋酶
釀酒酵母的eIF4A結構(1qva[1]
鑑定
標誌DEAD
PfamPF00270旧版
Pfam宗系CL0023旧版
InterPro英语InterProIPR011545
PROSITE英语PROSITEPDOC00039
SCOP英语Structural Classification of Proteins1qva / SUPFAM
CDD英语Conserved Domain Databasecd00268

DEAH家族與SKI2家族的蛋白序列也與DEAD box家族的蛋白相似[6][7][8],三者合稱DExD/H家族蛋白[9]

結構

1980年代晚期有學者發現許多蛋白的NTP結合位點英语NTP binding site序列和eIF4ARNA解旋酶的相似[10],後續研究發現這些蛋白均有9個保守的結構域,由N端C端分別為Q結構域、結構域I、結構域Ia、結構域Ib、結構域II、結構域III、結構域IV、結構域V與結構域VI,其中結構域II又名沃克結構域-B英语Walker motifs,包含天門冬胺酸-麩胺酸-丙胺酸-天門冬胺酸(DEAD)的氨基酸序列[2]。Q結構域、結構域I、結構域II與結構域VI為結合與水解ATP所需,結構域Ia、結構域Ib、結構域III、結構域IV與結構域V則為結合RNA所需[11]

功能

 
mRNA剪接過程,其中標註為橘色的蛋白皆屬DEAD box家族

DEAD box家族的蛋白多為RNA解旋酶,參與轉錄RNA剪接核糖體組裝英语ribosome biogenesis、RNA轉運、轉譯與RNA降解等細胞中的多種RNA相關反應[9][12][13]

釀酒酵母mRNA剪接的過程有Sub2、Prp28與Prp5等3種DEAD box蛋白參與[5],其中Prp5可與U2 SnRNA英语U2 spliceosomal RNA結合以影響其結構,使其得以與mRNA內含子中的分支位點(branchpoint)結合[14];Prp28可能可識別內含子的5′端切割位點,但此蛋白無解旋酶活性[15]。另外Prp2、Prp16、Prp22、Prp43與Brr213等多種DEAH家族蛋白也參與mRNA剪切[16]

轉譯起始因子eIF4A為一DEAD box蛋白,在轉譯起始時可解開mRNA5′ UTR二級結構,以利核糖體小次單元掃描mRNA以尋找起始密碼子[17]。另一DEAD box Ded1也參與轉譯起始過程,但具體機制仍不明[18];還有一與Ded1相似的DEAD box蛋白Vasa可與eIF2互動[19]

參考文獻

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