小柯机器人

美国弗吉尼亚大学医学院Edward H. Egelman研究组揭示原核生物鞭毛丝的超螺旋趋同演化。2022年9月2日，国际知名学术期刊《细胞》在线发表了这一成果。

冷冻电镜（cryo-EM）的进步使研究人员有可能直接观察到超螺旋的基础，研究人员展示了超螺旋的细菌和古细菌鞭毛的原子结构。对于细菌鞭毛丝，研究人员确定了11种不同的原丝构象，其中有三大类主体间的界面。对于古细菌鞭毛丝，10条原丝形成了一个由10种不同构象支持的超螺旋几何结构，其中一个原聚体间的不连续在弯曲内部形成了一个缝。这些结果表明，趋同演化产生了稳定的超螺旋几何形状，从而使微生物能够运动。

据悉，细菌和古细菌鞭毛丝的超螺旋是运动所需的。古细菌的鞭毛丝与细菌的鞭毛丝没有同源性，而是细菌的IV型菌毛的同源物。这些原核生物的鞭毛丝，每个都由数千份相同的亚单位组成，如何在扭转应力下形成稳定的超螺旋仍是一个谜题，而且其结构上的见解一直是难以理解的。

附：英文原文

Title: Convergent evolution in the supercoiling of prokaryotic flagellar filaments

Author: Mark A.B. Kreutzberger, Ravi R. Sonani, Junfeng Liu, Sharanya Chatterjee, Fengbin Wang, Amanda L. Sebastian, Priyanka Biswas, Cheryl Ewing, Weili Zheng, Frédéric Poly, Gad Frankel, B.F. Luisi, Chris R. Calladine, Mart Krupovic, Birgit E. Scharf, Edward H. Egelman

Issue&Volume: 2022-09-02

Abstract: The supercoiling of bacterial and archaeal flagellar filaments is required for motility.Archaeal flagellar filaments have no homology to their bacterial counterparts andare instead homologs of bacterial type IV pili. How these prokaryotic flagellar filaments,each composed of thousands of copies of identical subunits, can form stable supercoilsunder torsional stress is a fascinating puzzle for which structural insights havebeen elusive. Advances in cryoelectron microscopy (cryo-EM) make it now possible todirectly visualize the basis for supercoiling, and here, we show the atomic structuresof supercoiled bacterial and archaeal flagellar filaments. For the bacterial flagellarfilament, we identify 11 distinct protofilament conformations with three broad classesof inter-protomer interface. For the archaeal flagellar filament, 10 protofilamentsform a supercoil geometry supported by 10 distinct conformations, with one inter-protomerdiscontinuity creating a seam inside of the curve. Our results suggest that convergentevolution has yielded stable superhelical geometries that enable microbial locomotion.

DOI: 10.1016/j.cell.2022.08.009

Source: https://www.cell.com/cell/fulltext/S0092-8674(22)00996-5