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Sub-cellular Biochemistry

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https://www.readbyqxmd.com/read/28500535/reconstitution-of-protein-dynamics-involved-in-bacterial-cell-division
#1
Martin Loose, Katja Zieske, Petra Schwille
Even simple cells like bacteria have precisely regulated cellular anatomies, which allow them to grow, divide and to respond to internal or external cues with high fidelity. How spatial and temporal intracellular organization in prokaryotic cells is achieved and maintained on the basis of locally interacting proteins still remains largely a mystery. Bulk biochemical assays with purified components and in vivo experiments help us to approach key cellular processes from two opposite ends, in terms of minimal and maximal complexity...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28500534/the-tubulin-superfamily-in-archaea
#2
Christopher H S Aylett, Iain G Duggin
In comparison with bacteria and eukaryotes, the large and diverse group of microorganisms known as archaea possess a great diversity of cytoskeletal proteins, including members of the tubulin superfamily. Many species contain FtsZ, CetZ and even possible tubulins; however, some major taxonomic groups do not contain any member of the tubulin superfamily. Studies using the model archaeon, Halferax volcanii have recently been instrumental in defining the fundamental roles of FtsZ and CetZ in archaeal cell division and cell shape regulation...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28500533/archaeal-actin-family-filament-systems
#3
Ann-Christin Lindås, Karin Valegård, Thijs J G Ettema
Actin represents one of the most abundant and conserved eukaryotic proteins over time, and has an important role in many different cellular processes such as cell shape determination, motility, force generation, cytokinesis, amongst many others. Eukaryotic actin has been studied for decades and was for a long time considered a eukaryote-specific trait. However, in the early 2000s a bacterial actin homolog, MreB, was identified, characterized and found to have a cytoskeletal function and group within the superfamily of actin proteins...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28500532/the-structure-function-and-roles-of-the-archaeal-escrt-apparatus
#4
Rachel Y Samson, Megan J Dobro, Grant J Jensen, Stephen D Bell
Although morphologically resembling bacteria, archaea constitute a distinct domain of life with a closer affiliation to eukaryotes than to bacteria. This similarity is seen in the machineries for a number of essential cellular processes, including DNA replication and gene transcription. Perhaps surprisingly, given their prokaryotic morphology, some archaea also possess a core cell division apparatus that is related to that involved in the final stages of membrane abscission in vertebrate cells, the ESCRT machinery...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28500531/tubulin-like-proteins-in-prokaryotic-dna-positioning
#5
Gero Fink, Christopher H S Aylett
A family of tubulin-related proteins (TubZs) has been identified in prokaryotes as being important for the inheritance of virulence plasmids of several pathogenic Bacilli and also being implicated in the lysogenic life cycle of several bacteriophages. Cell biological studies and reconstitution experiments revealed that TubZs function as prokaryotic cytomotive filaments, providing one-dimensional motive forces. Plasmid-borne TubZ filaments most likely transport plasmid centromeric complexes by depolymerisation, pulling on the plasmid DNA, in vitro...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28500530/structure-and-dynamics-of-actin-like-cytomotive-filaments-in-plasmid-segregation
#6
Pananghat Gayathri, Shrikant Harne
One of the well-known functions of the bacterial cytoskeleton is plasmid segregation. Type II plasmid segregation systems, among the best characterized with respect to the mechanism of action, possess an actin-like cytomotive filament as the motor component. This chapter describes the essential components of the plasmid segregation machinery and their mechanism of action, concentrating on the actin-like protein family of the bacterial cytoskeleton. The structures of the actin-like filaments depend on their nucleotide state and these in turn contribute to the dynamics of the filaments...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28500529/bacterial-nucleoid-occlusion-multiple-mechanisms-for-preventing-chromosome-bisection-during-cell-division
#7
Maria A Schumacher
In most bacteria cell division is driven by the prokaryotic tubulin homolog, FtsZ, which forms the cytokinetic Z ring. Cell survival demands both the spatial and temporal accuracy of this process to ensure that equal progeny are produced with intact genomes. While mechanisms preventing septum formation at the cell poles have been known for decades, the means by which the bacterial nucleoid is spared from bisection during cell division, called nucleoid exclusion (NO), have only recently been deduced. The NO theory was originally posited decades ago based on the key observation that the cell division machinery appeared to be inhibited from forming near the bacterial nucleoid...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28500528/bacterial-actins
#8
Izoré, Fusinita van den Ent
A diverse set of protein polymers, structurally related to actin filaments contributes to the organization of bacterial cells as cytomotive or cytoskeletal filaments. This chapter describes actin homologs encoded by bacterial chromosomes. MamK filaments, unique to magnetotactic bacteria, help establishing magnetic biological compasses by interacting with magnetosomes. Magnetosomes are intracellular membrane invaginations containing biomineralized crystals of iron oxide that are positioned by MamK along the long-axis of the cell...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28500527/ftsz-ring-architecture-and-its-control-by-mincd
#9
Piotr Szwedziak, Debnath Ghosal
In bacteria and archaea, the most widespread cell division system is based on the tubulin homologue FtsZ protein, whose filaments form the cytokinetic Z-ring. FtsZ filaments are tethered to the membrane by anchors such as FtsA and SepF and are regulated by accessory proteins. One such set of proteins is responsible for Z-ring's spatiotemporal regulation, essential for the production of two equal-sized daughter cells. Here, we describe how our still partial understanding of the FtsZ-based cell division process has been progressed by visualising near-atomic structures of Z-rings and complexes that control Z-ring positioning in cells, most notably the MinCDE and Noc systems that act by negatively regulating FtsZ filaments...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28500526/intermediate-filaments-supporting-cell-shape-and-growth-in-bacteria
#10
Gabriella H Kelemen
For years intermediate filaments (IF), belonging to the third class of filamentous cytoskeletal proteins alongside microtubules and actin filaments, were thought to be exclusive to metazoan cells. Structurally these eukaryote IFs are very well defined, consisting of globular head and tail domains, which flank the central rod-domain. This central domain is dominated by an α-helical secondary structure predisposed to form the characteristic coiled-coil, parallel homo-dimer. These elementary dimers can further associate, both laterally and longitudinally, generating a variety of filament-networks built from filaments in the range of 10 nm in diameter...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28500525/ftsz-constriction-force-curved-protofilaments-bending-membranes
#11
Harold P Erickson, Masaki Osawa
FtsZ assembles in vitro into protofilaments (pfs) that are one subunit thick and ~50 subunits long. In vivo these pfs assemble further into the Z ring, which, along with accessory division proteins, constricts to divide the cell. We have reconstituted Z rings in liposomes in vitro, using pure FtsZ that was modified with a membrane targeting sequence to directly bind the membrane. This FtsZ-mts assembled Z rings and constricted the liposomes without any accessory proteins. We proposed that the force for constriction was generated by a conformational change from straight to curved pfs...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28500524/cytoskeletal-proteins-in-caulobacter-crescentus-spatial-orchestrators-of-cell-cycle-progression-development-and-cell-shape
#12
Kousik Sundararajan, Erin D Goley
Caulobacter crescentus, an aquatic Gram-negative α-proteobacterium, is dimorphic, as a result of asymmetric cell divisions that give rise to a free-swimming swarmer daughter cell and a stationary stalked daughter. Cell polarity of vibrioid C. crescentus cells is marked by the presence of a stalk at one end in the stationary form and a polar flagellum in the motile form. Progression through the cell cycle and execution of the associated morphogenetic events are tightly controlled through regulation of the abundance and activity of key proteins...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28500523/cell-cycle-machinery-in-bacillus-subtilis
#13
Jeff Errington, Ling Juan Wu
Bacillus subtilis is the best described member of the Gram positive bacteria. It is a typical rod shaped bacterium and grows by elongation in its long axis, before dividing at mid cell to generate two similar daughter cells. B. subtilis is a particularly interesting model for cell cycle studies because it also carries out a modified, asymmetrical division during endospore formation, which can be simply induced by starvation. Cell growth occurs strictly by elongation of the rod, which maintains a constant diameter at all growth rates...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28500522/e-coli-cell-cycle-machinery
#14
Joe Lutkenhaus, Shishen Du
Cytokinesis in E. coli is organized by a cytoskeletal element designated the Z ring. The Z ring is formed at midcell by the coalescence of FtsZ filaments tethered to the membrane by interaction of FtsZ's conserved C-terminal peptide (CCTP) with two membrane-associated proteins, FtsA and ZipA. Although interaction between an FtsZ monomer and either of these proteins is of low affinity, high affinity is achieved through avidity - polymerization linked CCTPs interacting with the membrane tethers. The placement of the Z ring at midcell is ensured by antagonists of FtsZ polymerization that are positioned within the cell and target FtsZ filaments through the CCTP...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28500521/overview-of-the-diverse-roles-of-bacterial-and-archaeal-cytoskeletons
#15
Linda A Amos, Jan Löwe
As discovered over the past 25 years, the cytoskeletons of bacteria and archaea are complex systems of proteins whose central components are dynamic cytomotive filaments. They perform roles in cell division, DNA partitioning, cell shape determination and the organisation of intracellular components. The protofilament structures and polymerisation activities of various actin-like, tubulin-like and ESCRT-like proteins of prokaryotes closely resemble their eukaryotic counterparts but show greater diversity. Their activities are modulated by a wide range of accessory proteins but these do not include homologues of the motor proteins that supplement filament dynamics to aid eukaryotic cell motility...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28271490/structure-and-assembly-of-clathrin-cages
#16
Mary Halebian, Kyle Morris, Corinne Smith
The unusual structure of clathrin, combined with its ability to assemble and disassemble rapidly in cells provides a model system for us to learn about the ways in which proteins can contribute mechanically to a functioning cell. In this article, we discuss the structural properties of clathrin cages and the triskelions which assemble to form them. The function of clathrin depends on the structure of these triskelions and the interactions they make both with each other during assembly and with the adaptor protein network that drives coated vesicle formation...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28271489/the-pyruvate-dehydrogenase-complex-and-related-assemblies-in-health-and-disease
#17
Olwyn Byron, John Gordon Lindsay
The family of 2-oxoacid dehydrogenase complexes (2-OADC), typified by the pyruvate dehydrogenase multi-enzyme complex (PDC) as its most prominent member, are massive molecular machines (Mr, 4-10 million) controlling key steps in glucose homeostasis (PDC), citric acid cycle flux (OGDC, 2-oxoglutarate dehydrogenase) and the metabolism of the branched-chain amino acids, leucine, isoleucine and valine (BCOADC, branched-chain 2-OADC). These highly organised mitochondrial arrays, composed of multiple copies of three separate enzymes, have been widely studied as paradigms for the analysis of enzyme cooperativity, substrate channelling, protein-protein interactions and the regulation of activity by phosphorylation ...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28271488/the-aminoacyl-trna-synthetase-complex
#18
Marc Mirande
Aminoacyl-tRNA synthetases (AARSs) are essential enzymes that specifically aminoacylate one tRNA molecule by the cognate amino acid. They are a family of twenty enzymes, one for each amino acid. By coupling an amino acid to a specific RNA triplet, the anticodon, they are responsible for interpretation of the genetic code. In addition to this translational, canonical role, several aminoacyl-tRNA synthetases also fulfill nontranslational, moonlighting functions. In mammals, nine synthetases, those specific for amino acids Arg, Asp, Gln, Glu, Ile, Leu, Lys, Met and Pro, associate into a multi-aminoacyl-tRNA synthetase complex, an association which is believed to play a key role in the cellular organization of translation, but also in the regulation of the translational and nontranslational functions of these enzymes...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28271487/groel-and-the-groel-groes-complex
#19
Noriyuki Ishii
Chaperonin is categorized as a molecular chaperone and mediates the formation of the native conformation of proteins by first preventing folding during synthesis or membrane translocation and subsequently by mediating the step-wise ATP-dependent release that result in proper folding. In the GroEL-GroES complex, a single heptameric GroEL ring binds one GroES ring in the presence of ATP/ADP, in this vein, the double ring GroEL tetradecamer is present in two distinct types of GroEL-GroES complexes: asymmetric 1:1 "bullet"-shaped GroEL:GroES and symmetric 1:2 "football" (American football)-shaped GroEL:GroES2...
2017: Sub-cellular Biochemistry
https://www.readbyqxmd.com/read/28271486/protein-complexes-in-the-nucleus-the-control-of-chromosome-segregation
#20
Victor M Bolanos-Garcia
Mistakes in the process of cell division can lead to the loss, gain or rearrangement of chromosomes. Significant chromosomal abnormalities are usually lethal to the cells and cause spontaneous miscarriages. However, in some cases, defects in the spindle assembly checkpoint lead to severe diseases, such as cancer and birth and development defects, including Down's syndrome. The timely and accurate control of chromosome segregation in mitosis relies on the spindle assembly checkpoint (SAC), an evolutionary conserved, self-regulated signalling system present in higher organisms...
2017: Sub-cellular Biochemistry
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