肌動蛋白存在于幾乎所有真核細(xì)胞中,，其形式有兩種：細(xì)絲狀F-肌動蛋白，它們驅(qū)動包括細(xì)胞運(yùn)動和肌肉收縮在內(nèi)的很多細(xì)胞過程,；以及它們由之而產(chǎn)生的單體,，即球形或G-肌動蛋白。在G-肌動蛋白向F-肌動蛋白轉(zhuǎn)變的過程中所發(fā)生的結(jié)構(gòu)變化仍然不清楚,，因為以前關(guān)于聚合物的模型一直在很大程度上以G-肌動蛋白的結(jié)構(gòu)為依據(jù),。
現(xiàn)在，F(xiàn)-肌動蛋白的結(jié)構(gòu)已以高分辨被確定,。該結(jié)構(gòu)顯示,，兩個主要區(qū)域（它們在G-肌動蛋白中形成一個推進(jìn)器一樣的纏繞結(jié)構(gòu)）沒有纏繞在一起，該分子在F-肌動蛋白中是平坦的,。平坦結(jié)構(gòu)與螺旋形排列相結(jié)合,，可穩(wěn)定鏈內(nèi)和鏈間的接觸。從G到F的構(gòu)形變化與以前關(guān)于肌動蛋白的生物化學(xué)研究完全一致,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 457, 441-445 (22 January 2008) | doi:10.1038/nature07685
The nature of the globular- to fibrous-actin transition
Toshiro Oda1,2, Mitsusada Iwasa2, Tomoki Aihara1, Yuichiro Maéda2,3 & Akihiro Narita3
1 X-ray Structural Analysis Research Team, RIKEN SPring-8 Center, RIKEN Harima Institute, 1-1-1, Kouto, Sayo, Hyogo 679-5148, Japan
2 ERATO project 'Actin-filament dynamics', Japan Science and Technology Agency (JST), 1-1-1, Kouto, Sayo, Hyogo 679-5148, Japan
3 Structural Biology Research Center and Division of Biological Science, Graduate School of Science, Nagoya University, Furo, Nagoya 464-8601, Japan
Actin plays crucial parts in cell motility through a dynamic process driven by polymerization and depolymerization, that is, the globular (G) to fibrous (F) actin transition. Although our knowledge about the actin-based cellular functions and the molecules that regulate the G- to F-actin transition is growing, the structural aspects of the transition remain enigmatic. We created a model of F-actin using X-ray fibre diffraction intensities obtained from well oriented sols of rabbit skeletal muscle F-actin to 3.3 ? in the radial direction and 5.6 ? along the equator. Here we show that the G- to F-actin conformational transition is a simple relative rotation of the two major domains by about 20 degrees. As a result of the domain rotation, the actin molecule in the filament is flat. The flat form is essential for the formation of stable, helical F-actin. Our F-actin structure model provides the basis for understanding actin polymerization as well as its molecular interactions with actin-binding proteins.
