在蛋白合成過程中,，轉(zhuǎn)移核糖核酸（轉(zhuǎn)移RNA，即tRNA）在其所附著的氨基酸被轉(zhuǎn)移到生長(zhǎng)中的肽鏈之上時(shí),，依次通過核糖體的A點(diǎn),、P點(diǎn)和E點(diǎn)。大尺度的構(gòu)形運(yùn)動(dòng)伴隨著它們的轉(zhuǎn)位,。
Holger Stark及其同事對(duì)核糖體數(shù)量驚人的190萬幅“單顆粒”冷電子顯微圖像進(jìn)行了處理,，以觀察這些動(dòng)態(tài)變化,。他們得出結(jié)論說，構(gòu)形變化是由熱驅(qū)動(dòng)的,，或者說是“布朗運(yùn)動(dòng)”,，所發(fā)生的變化引起tNRA在一個(gè)狹窄路徑上穿過核糖體做定向運(yùn)動(dòng)。(生物谷Bioon.net)
生物谷推薦原文出處：
Nature doi:10.1038/nature09206
Ribosome dynamics and tRNA movement by time-resolved electron cryomicroscopy
Niels Fischer, Andrey L. Konevega, Wolfgang Wintermeyer, Marina V. Rodnina & Holger Stark
The translocation step of protein synthesis entails large-scale rearrangements of the ribosome–transfer RNA (tRNA) complex. Here we have followed tRNA movement through the ribosome during translocation by time-resolved single-particle electron cryomicroscopy (cryo-EM). Unbiased computational sorting of cryo-EM images yielded 50 distinct three-dimensional reconstructions, showing the tRNAs in classical, hybrid and various novel intermediate states that provide trajectories and kinetic information about tRNA movement through the ribosome. The structures indicate how tRNA movement is coupled with global and local conformational changes of the ribosome, in particular of the head and body of the small ribosomal subunit, and show that dynamic interactions between tRNAs and ribosomal residues confine the path of the tRNAs through the ribosome. The temperature dependence of ribosome dynamics reveals a surprisingly flat energy landscape of conformational variations at physiological temperature. The ribosome functions as a Brownian machine that couples spontaneous conformational changes driven by thermal energy to directed movement.
