Advances in Structural Biology and the Application to Biological Filament Systems

Abstract

Structural biology has experienced several transformative technological advances in recent years. These include: development of extremely bright Xray sources (microfocus synchrotron beamlines and free electron lasers) and the use of electrons to extend protein crystallography to ever decreasing crystal sizes; and an increase in the resolution attainable by cryo-electron microscopy. Here we discuss the use of these techniques in general terms and highlight their application for biological filament systems, an area that is severely underrepresented in atomic resolution structures. We assemble a model of a capped tropomyosin-actin minifilament to demonstrate the utility of combining structures determined by different techniques. Finally, we survey the methods that attempt to transform high resolution structural biology into more physiological environments, such as the cell. Together these techniques promise a compelling decade for structural biology and, more importantly, they will provide exciting discoveries in understanding the designs and purposes of biological machines.

Structural evidence for the roles of divalent cations in actin polymerization and activation of ATP hydrolysis

“…There are more than 100 actin structures that have been solved using X-ray crystallography (73%), EM (25%), or fiber diffraction and electron crystallography (2%) deposited in the Protein Data Bank ( www.rcsb.org ). We inventoried all of the structures with a resolution of 2.5 Å or better (100% X-ray structures), resolutions at which cation binding can be predicted with some certainty ( 8 ), and cataloged the divalent cations bound to the outer surface of actin ( SI Appendix , Table S2 ). Some cation binding sites reoccurred in several structures ( Fig.…”

“…Although the structure of the filament has been determined by cryoelectron microscopy (cryoEM) at resolutions that allow interpretation of the architecture ( 7 ), understanding the chemistry of the filament, particularly the exact roles of nucleotides, water molecules, and cations in the processes of polymerization and depolymerization, is challenging at limited resolution. For example, even the highest resolution cryoEM filament map does not have sufficient detail to determine the H 2 O coordination of the ADP-bound Mg 2+ ( 7 , 8 ).…”

A graphene gold nanocomposite-based 5-FU drug and the enhancement of the MCF-7 cell line treatment

“…The results show that a level of about 0.5 aer 3 days is considered a very good ratio as compared to that in other studies, which exceeds an ROS level of 10; although this level is not sufficient to break the genetic materials in cells, via the cytotoxicity results, it can be understood that it causes necrosis and apoptotic death. [56][57][58] In addition, Fig. 6(a and b) show the effect of the rGO-Au-5-FU nanosystem samples on the viability of the MCF-7 cells cultured in six-well plates for one day and represent a comparison of the cytotoxic effect between all samples with different concentrations as well as pure 5-FU aer 72 hours of treatment.…”

Unconventional Imaging Methods to Capture Transient Structures during Actomyosin Interaction

“…Thanks to the recent developments of direct electron sensors and a number of automated procedures for image capturing and processing, the applicable size limit of the target objects in cryo-electron microscopy is getting lower and lower, approaching the theoretical limit of the technique [ 20 ]. Even with such a favorable amount of progress in cryo-EM techniques, their application to the structural analysis of actomyosin might be hampered by several obstacles.…”