k原核生物的轉(zhuǎn)錄ppt課件(參考版)
2025-05-15 05:33本頁面
【正文】 RNA polymerase/transcription and DNA polymerase/replication RNA pol DNA pol Template dsDNA is better ss/dsDNA Require primer No Yes Initiation promoter origin elongation 40 nt/ sec 900 bp/sec terminator Synthesized RNA Template DNA Summary: 1. General features of RNA pol. 2. E. coli RNA pol: holoenzyme (?2? ?’?s) and core enzyme (?2? ?’?). Role of sigma factor. 3. E. coli s70 promoter: 35 sequence (TTGACA), 10 (TATAAT), amp。 E. coli polymerase: ? subunit 1. Encoded by the rpoC gene . 2. Binds two Zn 2+ ions and may participate in the catalytic function of the polymerase ? Heparin (肝素 )： binds to the ?’ subunit 體外抑制轉(zhuǎn)錄 . ? Heparin petes with DNA for binding to the polymerase. 3. ?’ subunit may be responsible for binding to the template DNA （與模板結(jié)合有關(guān)） . E. coli polymerase: ?’ subunit 1. Many 原核生物 contain multiple s factors to recognize different promoters. The most mon s factor in E. coli is s70. 2. Binding of the s factor converts the core RNA pol into the holoenzyme. E. coli polymerase: s factor 1. s factor is critical in promoter recognition, by decreasing 核心酶對非特異序列的親和力 (104) and increasing the affinity for the corresponding promoter 2. s factor is released from the RNA pol after initiation (RNA chain is 89 nt) 3. s factor 數(shù)目明顯少于 the other subunits of the RNA pol（ 30%） . E. coli polymerase: s factor K3 The E. coli σ70 promoter 1. Promoter sequences: 10 sequence and 35 sequence 2. Transcription start site 3. Promoter efficiency Promoters: 含有 RNA pol 特異性結(jié)合和轉(zhuǎn)錄起始所需的保守序列。 延伸 起始 only KD KD 151 KD 155 KD 11 KD 70 KD 465kd ? RNA synthesis rate: 40 nt per second at 37oC ? 非球形結(jié)構(gòu)，圓柱形孔道旁有一突起，孔道大小表明 the enzyme plex can bind directly to 16 bp of DNA. The whole polymerase binds over 60 bp. E. coli RNA polymerase: 全酶 : ?2? ?’?s for initiation 核心酶 : ?2? ?’? for elongation RNA pol 亞基 E. coli polymerase: ? subunit ? Two identical subunits in the core enzyme ? Encoded by the rpoA gene ? Required for core protein assembly ? May play a role
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