Geometry of the T-Even Bacteriophage Head

1972 ◽  
Vol 30 ◽  
pp. 202-203
Author(s):  
C. N. Gordon
Keyword(s):  
Icosahedral Symmetry ◽  
Geometrical Shape ◽  
Middle Section ◽  
Head Shape ◽  
Protein Subunits ◽  
Complex Process ◽  
Phage Dna ◽  
Head Assembly

The T-even bacteriophage head is a non-isometric structure composed of more than one kind of protein. The head is assembled in a complex process which involves several products of the phage DNA, and probably the participation of the DNA itself. Two problems which are as yet unsolved are the manner in which the protein subunits are arranged in the mature phage head and the mechanism of head assembly.There are two conflicting theories regarding the geometrical shape of the head: Moody and Boy de la Tour and Kellenberger consider the head shape to be a bipyramidal pentagonal, antiprism (“prolate icosahedron“); this structure can be thought of as being derived from a head with regular icosahedral symmetry by lengthwise extension of the middle section.

scholarly journals Structure of a headful DNA-packaging bacterial virus at 2.9 Å resolution by electron cryo-microscopy

2017 ◽  
Vol 114 (14) ◽  
pp. 3601-3606 ◽  
Author(s):  
Haiyan Zhao ◽  
Kunpeng Li ◽  
Anna Y. Lynn ◽  
Keith E. Aron ◽  
Guimei Yu ◽  
...  
Keyword(s):  
Self Assembly ◽  
Noncovalent Interactions ◽  
Dna Packaging ◽  
Protein Subunits ◽  
Significant Strength ◽  
Phage Dna ◽  
Mortise And Tenon ◽  
Α Helix ◽  
Β Sheet ◽  
Protein Shell

The enormous prevalence of tailed DNA bacteriophages on this planet is enabled by highly efficient self-assembly of hundreds of protein subunits into highly stable capsids. These capsids can stand with an internal pressure as high as ∼50 atmospheres as a result of the phage DNA-packaging process. Here we report the complete atomic model of the headful DNA-packaging bacteriophage Sf6 at 2.9 Å resolution determined by electron cryo-microscopy. The structure reveals the DNA-inflated, tensed state of a robust protein shell assembled via noncovalent interactions. Remarkable global conformational polymorphism of capsid proteins, a network formed by extended N arms, mortise-and-tenon–like intercapsomer joints, and abundant β-sheet–like mainchain:mainchain intermolecular interactions, confers significant strength yet also flexibility required for capsid assembly and DNA packaging. Differential formations of the hexon and penton are mediated by a drastic α–helix-to-β–strand structural transition. The assembly scheme revealed here may be common among tailed DNA phages and herpesviruses.

scholarly journals Assembly and Intracellular Targeting of the βγ Subunits of Heterotrimeric G Proteins

1997 ◽  
Vol 137 (2) ◽  
pp. 305-317 ◽  
Author(s):  
Armin Rehm ◽  
Hidde L. Ploegh
Keyword(s):  
Plasma Membrane ◽  
Membrane Trafficking ◽  
Brefeldin A ◽  
Heterotrimeric G Proteins ◽  
Protein Subunits ◽  
Intracellular Targeting ◽  
Complex Process ◽  
Guanine Nucleotide Binding ◽  
Nucleotide Binding Proteins ◽  
Guanine Nucleotide Binding Proteins

The assembly in living cells of heterotrimeric guanine nucleotide binding proteins from their constituent α, β, and γ subunits is a complex process, compounded by the multiplicity of the genes that encode them, and the diversity of receptors and effectors with which they interact. Monoclonal anti-β antibodies (ARC5 and ARC9), raised against immunoaffinity purified βγ complexes, recognize β subunits when not associated with γ and can thus be used to monitor assembly of βγ complexes. Complex formation starts immediately after synthesis and is complete within 30 min. Assembly occurs predominantly in the cytosol, and association of βγ complexes with the plasma membrane fraction starts between 15–30 min of chase. Three pools of β subunits can be distinguished based on their association with γ subunits, their localization, and their detergent solubility. Association of β and α subunits with detergent-insoluble domains occurs within 1 min of chase, and increases to reach a plateau of near complete detergent resistance within 30 min of chase. Brefeldin A treatment does not interfere with delivery of βγ subunits to detergent-insoluble domains, suggesting that assembly of G protein subunits with their receptors occurs distally from the BFA-imposed block of intracellular membrane trafficking and may occur directly at the plasma membrane.

scholarly journals Subassemblies and Asymmetry in Assembly of Herpes Simplex Virus Procapsid

mBio ◽  
2015 ◽  
Vol 6 (5) ◽  
Author(s):  
Anastasia A. Aksyuk ◽  
William W. Newcomb ◽  
Naiqian Cheng ◽  
Dennis C. Winkler ◽  
Juan Fontana ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Building Blocks ◽  
Scaffolding Protein ◽  
Icosahedral Symmetry ◽  
Large Set ◽  
Protein Subunits ◽  
Cryo Electron Microscopy ◽  
Simplex Virus

ABSTRACTThe herpes simplex virus 1 (HSV-1) capsid is a massive particle (~200 MDa; 1,250-Å diameter) with T=16 icosahedral symmetry. It initially assembles as a procapsid with ~4,000 protein subunits of 11 different kinds. The procapsid undergoes major changes in structure and composition as it matures, a process driven by proteolysis and expulsion of the internal scaffolding protein. Assembly also relies on an external scaffolding protein, the triplex, an α2β heterotrimer that coordinates neighboring capsomers in the procapsid and becomes a stabilizing clamp in the mature capsid. To investigate the mechanisms that regulate its assembly, we developed a novel isolation procedure for the metastable procapsid and collected a large set of cryo-electron microscopy data. In addition to procapsids, these preparations contain maturation intermediates, which were distinguished by classifying the images and calculating a three-dimensional reconstruction for each class. Appraisal of the procapsid structure led to a new model for assembly; in it, the protomer (assembly unit) consists of one triplex, surrounded by three major capsid protein (MCP) subunits. The model exploits the triplexes’ departure from 3-fold symmetry to explain the highly skewed MCP hexamers, the triplex orientations at each 3-fold site, and the T=16 architecture. These observations also yielded new insights into maturation.IMPORTANCEThis paper addresses the molecular mechanisms that govern the self-assembly of large, structurally complex, macromolecular particles, such as the capsids of double-stranded DNA viruses. Although they may consist of thousands of protein subunits of many different kinds, their assembly is precise, ranking them among the largest entities in the biosphere whose structures are uniquely defined to the atomic level. Assembly proceeds in two stages: formation of a precursor particle (procapsid) and maturation, during which major changes in structure and composition take place. Our analysis of the HSV procapsid by cryo-electron microscopy suggests a hierarchical pathway in which multisubunit “protomers” are the building blocks of the procapsid but their subunits are redistributed into different subcomplexes upon being incorporated into a nascent procapsid and are redistributed again in maturation. Assembly is a highly virus-specific process, making it a potential target for antiviral intervention.

Experiment Solution Velocity and Pressure Field in the Mixing Process Computer Simulation

2014 ◽  
Vol 693 ◽  
pp. 68-73
Author(s):  
Helena Kravarikova
Keyword(s):  
Rotation Axis ◽  
Flow Density ◽  
Geometrical Shape ◽  
Technical Equipment ◽  
Mixing Process ◽  
Rotational Movement ◽  
Complex Process ◽  
Axis Of Symmetry ◽  
Process Computer ◽  
Solution Velocity

The process of mixing materials is a very complex process. The mixing process is used for homogenisation of substances. Rather than propose a real mixer, you must first construct a mixer for operational purposes experimental solutions. Experimental solutions are most often realized in laboratory conditions. Experimental mixers are made according to the requirements of power mixers, fluid flow, density and viscosity of the mixed fluid. To investigate the mixing process in the Laboratory mixers are made on the basis of the criteria of non-dimensional simplex. For designing operating mixers can also use analytical solutions of technical equipment and the mixing process. It is now possible to implement solutions using FEM numerical simulation of this phenomenon.The homogeneity of the mixed substances, mixer performs rotational movement about the axis of rotation. In most cases, the rotational movement of the stirrer describes the geometrical shape of the mixer. Usually rotation axis Mixer is the axis of symmetry. The shape and dimensions of the stirrer depends on the desired performance of mixer, the type of flow, the type and quantity of mixed materials.

scholarly journals Assembly and Disassembly of Viral Capsids

2005 ◽  
Vol 6 (2) ◽  
pp. 69-72 ◽  
Author(s):  
Roya Zandi ◽  
David Reguera ◽  
Robijn Bruinsma ◽  
William Gelbart ◽  
Joseph Rudnick
Keyword(s):  
Viral Genome ◽  
Release Mechanism ◽  
Icosahedral Symmetry ◽  
Hamiltonian Approach ◽  
Conformational Switching ◽  
Viral Capsids ◽  
Protein Subunits ◽  
Single Protein ◽  
Shed Light

We address here a theoretical basis for the icosahedral symmetry that is observed so commonly for viral capsids, i.e., the single-protein-thick rigid shells that protect the viral genome. In particular, we outline the phenomenological hamiltonian approach developed recently (see Zandi, R., Reguera, D., Bruinsma, R., Gelbart, W.M. and Rudnick, J. (2004), Original of icosahedral symmetry in viruses,Proc. Natl. Acad. Sci., 101, 15556–15560) to account for the overwhelming prevalence of the Caspar-Klug “T-number” structures that are found for “spherical” viruses. We feature the role of “conformational switching energies” defining the competing multimeric states of the protein subunits. The results of Monte Carlo simulation of this model are argued to shed light as well on the mechanical properties and genome release mechanism for these viruses.

scholarly journals Lamin A/C proteins in the spermatid acroplaxome are essential in mouse spermiogenesis

Reproduction ◽  
2014 ◽  
Vol 148 (5) ◽  
pp. 479-487 ◽  
Author(s):  
Jian Shen ◽  
Wen Chen ◽  
Binbin Shao ◽  
Yujuan Qi ◽  
Zhengrong Xia ◽  
...  
Keyword(s):  
Expression Profiles ◽  
Sperm Head ◽  
Mature Sperm ◽  
Lamin A ◽  
Head Shape ◽  
Functional Development ◽  
Complex Process ◽  
Acrosome Formation ◽  
Protein Expression Profiles ◽  
Negative Controls

Spermiogenesis is a complex process of terminal differentiation that is necessary to produce mature sperm. Using protein expression profiles of mouse and human testes generated from our previous studies, we chose to examine the actions of lamin A/C in the current investigation. Lamin A and lamin C are isoforms of the A-type lamins that are encoded by theLMNAgene. Our results showed that lamin A/C was expressed in the mouse testis throughout the different stages of spermatogenesis and in mature sperm. Lamin A/C was also expressed in mouse haploid germ cells and was found to be localized to the acroplaxome in spermiogenesis, from round spermatids until mature spermatozoa. The decreased expression of lamin A/C following injections of siRNA againstLmnacaused a significant increase in caudal sperm head abnormalities when compared with negative controls. These abnormalities were characterized by increased fragmentation of the acrosome and abnormal vesicles, which failed to fuse to the developing acrosome. This fragmentation also caused significant alterations in nuclear elongation and acrosome formation. Furthermore, we found that lamin A/C interacted with the microtubule plus-end-tracking protein CLIP170. These results suggest that lamin A/C is critical for proper structural and functional development of the sperm acrosome and head shape.

Replication of Bacteriophage 186 DNA

1972 ◽  
Vol 30 ◽  
pp. 194-195
Author(s):  
Dhruba K. Chattoraj ◽  
Ross B. Inman
Keyword(s):  
Electron Microscopy ◽  
Dna Replication ◽  
Frame Of Reference ◽  
Dna Molecules ◽  
E Coli ◽  
Phage Dna ◽  
Partial Denaturation

Electron microscopy of replicating intermediates has been quite useful in understanding the mechanism of DNA replication in DNA molecules of bacteriophage, mitochondria and plasmids. The use of partial denaturation mapping has made the tool more powerful by providing a frame of reference by which the position of the replicating forks in bacteriophage DNA can be determined on the circular replicating molecules. This provided an easy means to find the origin and direction of replication in λ and P2 phage DNA molecules. DNA of temperate E. coli phage 186 was found to have an unique denaturation map and encouraged us to look into its mode of replication.

Imaging of Al-Li-Cu alloys with a Scanning Ion Microprobe

1990 ◽  
Vol 48 (2) ◽  
pp. 314-315
Author(s):  
K.K. Soni ◽  
D.B. Williams ◽  
J.M. Chabala ◽  
R. Levi-Setti ◽  
D.E. Newbury
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Equilibrium Phase ◽  
Icosahedral Symmetry ◽  
Ion Microprobe ◽  
X Ray ◽  
Cu Alloys ◽  
Two Phases ◽  
The University ◽  
Secondary Ion

In contrast to the inability of x-ray microanalysis to detect Li, secondary ion mass spectrometry (SIMS) generates a very strong Li+ signal. The latter’s potential was recently exploited by Williams et al. in the study of binary Al-Li alloys. The present study of Al-Li-Cu was done using the high resolution scanning ion microprobe (SIM) at the University of Chicago (UC). The UC SIM employs a 40 keV, ∼70 nm diameter Ga+ probe extracted from a liquid Ga source, which is scanned over areas smaller than 160×160 μm2 using a 512×512 raster. During this experiment, the sample was held at 2 × 10-8 torr.In the Al-Li-Cu system, two phases of major importance are T1 and T2, with nominal compositions of Al2LiCu and Al6Li3Cu respectively. In commercial alloys, T1 develops a plate-like structure with a thickness <∼2 nm and is therefore inaccessible to conventional microanalytical techniques. T2 is the equilibrium phase with apparent icosahedral symmetry and its presence is undesirable in industrial alloys.

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