Unique Properties of Eukaryote-Type Actin and Profilin Horizontally Transferred to Cyanobacteria

A eukaryote-type actin and its binding protein profilin encoded on a genomic island in the cyanobacterium Microcystis aeruginosa PCC 7806 co-localize to form a hollow, spherical enclosure occupying a considerable intracellular space as shown by in vivo fluorescence microscopy. Biochemical and biophysical characterization reveals key differences between these proteins and their eukaryotic homologs. Small-angle X-ray scattering shows that the actin assembles into elongated, filamentous polymers which can be visualized microscopically with fluorescent phalloidin. Whereas rabbit actin forms thin cylindrical filaments about 100 µm in length, cyanobacterial actin polymers resemble a ribbon, arrest polymerization at 5-10 µm and tend to form irregular multi-strand assemblies. While eukaryotic profilin is a specific actin monomer binding protein, cyanobacterial profilin shows the unprecedented property of decorating actin filaments. Electron micrographs show that cyanobacterial profilin stimulates actin filament bundling and stabilizes their lateral alignment into heteropolymeric sheets from which the observed hollow enclosure may be formed. We hypothesize that adaptation to the confined space of a bacterial cell devoid of binding proteins usually regulating actin polymerization in eukaryotes has driven the co-evolution of cyanobacterial actin and profilin, giving rise to an intracellular entity

Management of cytoskeleton architecture by molecular chaperones and immunophilins

Cytoskeletal structure is continually remodeled to accommodate normal cell growth and to respond to pathophysiological cues. As a consequence, several cytoskeleton-interacting proteins become involved in a variety of cellular processes such as cell growth and division, cell movement, vesicle transportation, cellular organelle location and function, localization and distribution of membrane receptors, and cell-cell communication. Molecular chaperones and immunophilins are counted among the most important proteins that interact closely with the cytoskeleton network, in particular with microtubules and microtubule-associated factors. In several situations, heat-shock proteins and immunophilins work together as a functionally active heterocomplex, although both types of proteins also show independent actions. In circumstances where homeostasis is affected by environmental stresses or due to genetic alterations, chaperone proteins help to stabilize the system. Molecular chaperones facilitate the assembly, disassembly and/or folding/refolding of cytoskeletal proteins, so they prevent aberrant protein aggregation. Nonetheless, the roles of heat-shock proteins and immunophilins are not only limited to solve abnormal situations, but they also have an active participation during the normal differentiation process of the cell and are key factors for many structural and functional rearrangements during this course of action. Cytoskeleton modifications leading to altered localization of nuclear factors may result in loss- or gain-of-function of such factors, which affects the cell cycle and cell development. Therefore, cytoskeletal components are attractive therapeutic targets, particularly microtubules, to prevent pathological situations such as rapidly dividing tumor cells or to favor the process of cell differentiation in other cases. In this review we will address some classical and novel aspects of key regulatory functions of heat-shock proteins and immunophilins as housekeeping factors of the cytoskeletal network.Fil: Quintá, Héctor Ramiro. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); ArgentinaFil: Galigniana, Natalia Maricel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); ArgentinaFil: Erlejman, Alejandra Giselle. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; ArgentinaFil: Lagadari, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); ArgentinaFil: Piwien Pilipuk, Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); ArgentinaFil: Galigniana, Mario Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentin

Diversité phénotypique de l’âne domestique (Equus africanus asinus) dans la région des hautes terres du nord oust Cameroun

L’objectif général du travail était de contribuer à une meilleure connaissance de la diversité des ânes en vue de son exploitation rationnelle et plus spécifiquement, d’évaluer la variabilité morphobiométrique et d’en déduire la structure et les relations phylogénétique des ânes dans la région. A cet effet, un échantillon de 174 ânes adultes (96 mâles et 78 femelles) a été observé dans 7 localités. Les résultats montrent que sur le plan phanéroptique, la robe grise est dominante (86,2%) et la robe baie brûlé moins représentée (0,5%). Les mensurations corporelles et leur moyenne ont été la hauteur au garrot (HG) 99,73±3,57 cm, le pourtour thoracique (PT) 108,66±5,08 cm, la largeur de la poitrine 25,85±2,62 cm, la profondeur de la poitrine 48,80±3,97 cm, la longueur du corps(LC) 110,07±6,06 cm, la hauteur à la croupe 103,28±3,91 cm, le pourtour du canon 14,95±1,85 cm, le poids vif (PV) est de 128,68 ± 17,07 kg. Les corrélations sont significatives (P<0,01), positives et presque parfaites entre le PV et le PT (r=0,99). L’équation de prédiction du poids vif PV=2,34PT-233,89 semble être la meilleure, car elle est simple et son coefficient de détermination est élevé (R2=0,99). Les indices corporel de profil et relatif sont respectivement de 0,91±0,04 et 1,01±0,05 et permettent de classer les ânes des hautes terres du Nord-Ouest Cameroun comme longilignes. L’indice dactylo-thoracique est de 0,14±0,04 et suggère que les ânes sont de type hypermétrique. Le PV et la LC contribuent à 59,76% à la variabilité génétique au sein de la population. L’analyse factorielle discriminante montre que la population est constituée de 3 types génétiques A, B et C. L’arbre phylogénétique révèle que les types génétique A et C sont génétiquement plus reproche et plus distant du type génétique B. La variabilité observée suggère des possibilités d’amélioration génétique des ânes des hautes terres du Nord-Ouest Cameroun.Mots clés : Asins, Biodiversité, phénotype, indice biométrique, Camerou

The actin-like MreB cytoskeleton organizes viral DNA replication in bacteria

Little is known about the organization or proteins involved in membrane-associated replication of prokaryotic genomes. Here we show that the actin-like MreB cytoskeleton of the distantly related bacteria Escherichia coli and Bacillus subtilis is required for efficient viral DNA replication. Detailed analyses of B. subtilis phage ϕ29 showed that the MreB cytoskeleton plays a crucial role in organizing phage DNA replication at the membrane. Thus, phage double-stranded DNA and components of the ϕ29 replication machinery localize in peripheral helix-like structures in a cytoskeleton-dependent way. Importantly, we show that MreB interacts directly with the ϕ29 membrane-protein p16.7, responsible for attaching viral DNA at the cell membrane. Altogether, the results reveal another function for the MreB cytoskeleton and describe a mechanism by which viral DNA replication is organized at the bacterial membrane

Viral terminal protein directs early organization of phage DNA replication at the bacterial nucleoid

The mechanism leading to protein-primed DNA replication has been studied extensively in vitro. However, little is known about the in vivo organization of the proteins involved in this fundamental process. Here we show that the terminal proteins (TPs) of phages ϕ29 and PRD1, infecting the distantly related bacteria Bacillus subtilis and Escherichia coli, respectively, associate with the host bacterial nucleoid independently of other viral-encoded proteins. Analyses of phage ϕ29 revealed that the TP N-terminal domain (residues 1–73) possesses sequence-independent DNA-binding capacity and is responsible for its nucleoid association. Importantly, we show that in the absence of the TP N-terminal domain the efficiency of ϕ29 DNA replication is severely affected. Moreover, the TP recruits the phage DNA polymerase to the bacterial nucleoid, and both proteins later are redistributed to enlarged helix-like structures in an MreB cytoskeleton-dependent way. These data disclose a key function for the TP in vivo: organizing the early viral DNA replication machinery at the cell nucleoid

Helicobacter pyloriPossesses Four Coiled-Coil-Rich Proteins That Form Extended Filamentous Structures and Control Cell Shape and Motility ▿

We identified two additional genes of Helicobacter pyloriencoding Ccrp proteins. All four Ccrps have different multimerization and filamentation properties and different types of smallest subunits and do not copurify, suggesting a system of individual Ccrp filaments. Despite the presence of morphologically unaltered flagella, all ccrpmutants displayed significantly reduced motility