scholarly journals Human 76p

1999 ◽  
Vol 147 (4) ◽  
pp. 857-868 ◽  
Author(s):  
Fabienne Fava ◽  
Brigitte Raynaud-Messina ◽  
Jeanne Leung-Tack ◽  
Laurent Mazzolini ◽  
Min Li ◽  
...  
Keyword(s):  
Molecular Level ◽  
Basal Bodies ◽  
Microtubule Nucleation ◽  
Higher Plant ◽  
Spindle Poles ◽  
Mammalian Tissues ◽  
Associated Proteins ◽  
Centrosomal Proteins ◽  
Polypeptide Band

The role of the centrosomes in microtubule nucleation remains largely unknown at the molecular level. γ-Tubulin and the two associated proteins h103p (hGCP2) and h104p (hGCP3) are essential. These proteins are also present in soluble complexes containing additional polypeptides. Partial sequencing of a 76- kD polypeptide band from these complexes allowed the isolation of a cDNA encoding for a new protein (h76p = hGCP4) expressed ubiquitously in mammalian tissues. Orthologues of h76p have been characterized in Drosophila and in the higher plant Medicago. Several pieces of evidence indicate that h76p is involved in microtubule nucleation. (1) h76p is localized at the centrosome as demonstrated by immunofluorescence. (2) h76p and γ-tubulin are associated in the γ-tubulin complexes. (3) γ-tubulin complexes containing h76p bind to microtubules. (4) h76p is recruited to the spindle poles and to Xenopus sperm basal bodies. (5) h76p is necessary for aster nucleation by sperm basal bodies and recombinant h76p partially replaces endogenous 76p in oocyte extracts. Surprisingly, h76p shares partial sequence identity with human centrosomal proteins h103p and h104p, suggesting a common protein core. Hence, human γ-tubulin appears associated with at least three evolutionary related centrosomal proteins, raising new questions about their functions at the molecular level.

scholarly journals Recruitment of the γ-Tubulin Ring Complex to Drosophila Salt-stripped Centrosome Scaffolds

1998 ◽  
Vol 142 (3) ◽  
pp. 775-786 ◽  
Author(s):  
Michelle Moritz ◽  
Yixian Zheng ◽  
Bruce M. Alberts ◽  
Karen Oegema
Keyword(s):  
Soluble Fraction ◽  
Protein Complexes ◽  
Drosophila Embryo ◽  
Microtubule Nucleation ◽  
Complementation Assay ◽  
Embryo Extract ◽  
Ring Complex ◽  
Centrosomal Proteins

Extracting isolated Drosophila centrosomes with 2 M KI generates salt-resistant scaffolds that lack the centrosomal proteins CP190, CP60, centrosomin, and γ-tubulin. To clarify the role of these proteins in microtubule nucleation by centrosomes and to identify additional centrosome components required for nucleation, we have developed an in vitro complementation assay for centrosome function. Centrosome aster formation is reconstituted when these inactive, salt-stripped centrosome scaffolds are supplemented with a soluble fraction of a Drosophila embryo extract. The CP60 and CP190 can be removed from this extract without effect, whereas removing the γ-tubulin destroys the complementing activity. Consistent with these results, we find no evidence that these three proteins form a complex together. Instead, γ-tubulin is found in two distinct protein complexes of 240,000 and ∼3,000,000 D. The larger complex, which is analogous to the Xenopus γ-tubulin ring complex (γTuRC) (Zheng, Y., M.L. Wong, B. Alberts, and T. Mitchison. 1995. Nature. 378:578–583), is necessary but not sufficient for complementation. An additional factor found in the extract is required. These results provide the first evidence that the γTuRC is required for microtubule nucleation at the centrosome.

Role of tubulin-associated proteins in microtubule nucleation and elongation

1977 ◽  
Vol 117 (1) ◽  
pp. 33-52 ◽  
Author(s):  
Douglas B. Murphy ◽  
Kenneth A. Johnson ◽  
Gary G. Borisy
Keyword(s):  
Microtubule Nucleation ◽  
Associated Proteins

Focusing on spindle poles

1998 ◽  
Vol 111 (11) ◽  
pp. 1477-1481 ◽  
Author(s):  
D.A. Compton
Keyword(s):  
Light Microscopy ◽  
Dominant Role ◽  
Cell Types ◽  
Common Mechanism ◽  
Microtubule Nucleation ◽  
Specialized Cell ◽  
Spindle Poles ◽  
Meiotic Spindles ◽  
Centrosomal Proteins

Spindle poles are discernible by light microscopy as the sites where microtubules converge at the ends of both mitotic and meiotic spindles. In most cell types centrosomes are present at spindle poles due to their dominant role in microtubule nucleation. However, in some specialized cell types microtubules converge into spindle poles in the absence of centrosomes. Thus, spindle poles in centrosomal and acentrosomal cell types are structurally different, and it is this structural dichotomy that has created confusion as to the mechanism by which microtubules are organized into spindle poles. This review summarizes a series of recent articles that begin to resolve this confusion by demonstrating that spindle poles are organized through a common mechanism by a conserved group of non-centrosomal proteins in the presence or absence of centrosomes.

scholarly journals A human centrosomal protein is immunologically related to basal body-associated proteins from lower eucaryotes and is involved in the nucleation of microtubules.

1991 ◽  
Vol 115 (1) ◽  
pp. 129-140 ◽  
Author(s):  
M Moudjou ◽  
M Paintrand ◽  
B Vigues ◽  
M Bornens
Keyword(s):  
Cultured Cells ◽  
The Other ◽  
Basal Bodies ◽  
Immunocytochemical Localization ◽  
Specific Function ◽  
Animal Cells ◽  
Structural Element ◽  
Centrosomal Protein ◽  
Associated Proteins ◽  
Centrosomal Proteins

Isolation of centrosomes from human cells has revealed a proteic pattern which is both complex and specific. As the most prominent structural element of centrosomes in animal cells, the centriole which is present as two copies, is a highly conserved structure, we have attempted to identify centrosomal proteins on the basis of immunocross-reaction with proteins identified in basal bodies from lower eucaryotes. We report that two antibodies, one raised against the Ca(+)-binding protein centrin (Salisbury, J. L., A. T. Baron, B. Surek, and M. Melkonian. 1984. J. Cell Biol. 99:962-970) and the other directed against a 230-kD protein isolated from the infraciliary cytoskeletal lattice of the protozoan Polyplastron m., decorate the centrosome of human cultured cells, and identify one of the major centrosomal components revealed as a doublet of 62/64 kD. Moreover the nucleation reaction of microtubules, which can be efficiently produced on isolated centrosomes, is blocked by the antibodies, a result which strongly implicates the 62/64-kD protein in this centrosomal activity. We also show that the 62/64-kD protein remains insoluble in conditions (0.5 M KI or 8 M urea) which are capable of extracting most of the centrosomal proteins. Immunocytochemical localization by EM of isolated centrosomes revealed the association of this 62/64-kD doublet with the intercentriolar link and the pericentriolar lattice. Our results suggest that conservation of structure in the centrosome from divergent organisms could be matched by conservation of proteins and activity, evidence for the maintenance of a specific function, which could involve Ca2+, associated with the microtubule organizing centers.

scholarly journals The Drosophila Protein Asp Is Involved in Microtubule Organization during Spindle Formation and Cytokinesis

2001 ◽  
Vol 153 (4) ◽  
pp. 637-648 ◽  
Author(s):  
James G. Wakefield ◽  
Silvia Bonaccorsi ◽  
Maurizio Gatti
Keyword(s):  
Colchicine Treatment ◽  
Spindle Pole ◽  
Mitotic Spindles ◽  
Microtubule Nucleation ◽  
Phenotypic Analysis ◽  
Microtubule Organization ◽  
Central Spindle ◽  
Spindle Poles ◽  
Drosophila Protein

Abnormal spindle (Asp) is a 220-kD microtubule-associated protein from Drosophila that has been suggested to be involved in microtubule nucleation from the centrosome. Here, we show that Asp is enriched at the poles of meiotic and mitotic spindles and localizes to the minus ends of central spindle microtubules. Localization to these structures is independent of a functional centrosome. Moreover, colchicine treatment disrupts Asp localization to the centrosome, indicating that Asp is not an integral centrosomal protein. In both meiotic and mitotic divisions of asp mutants, microtubule nucleation occurs from the centrosome, and γ-tubulin localizes correctly. However, spindle pole focusing and organization are severely affected. By examining cells that carry mutations both in asp and in asterless, a gene required for centrosome function, we have determined the role of Asp in the absence of centrosomes. Phenotypic analysis of these double mutants shows that Asp is required for the aggregation of microtubules into focused spindle poles, reinforcing the conclusion that its function at the spindle poles is independent of any putative role in microtubule nucleation. Our data also suggest that Asp has a role in the formation of the central spindle. The inability of asp mutants to correctly organize the central spindle leads to disruption of the contractile ring machinery and failure in cytokinesis.

scholarly journals Regulating the transition from centriole to basal body

2011 ◽  
Vol 193 (3) ◽  
pp. 435-444 ◽  
Author(s):  
Tetsuo Kobayashi ◽  
Brian D. Dynlacht
Keyword(s):  
Cell Cycle ◽  
Basal Body ◽  
Primary Cilia ◽  
Molecular Mechanisms ◽  
Basal Bodies ◽  
Spindle Poles ◽  
Shed Light

The role of centrioles changes as a function of the cell cycle. Centrioles promote formation of spindle poles in mitosis and act as basal bodies to assemble primary cilia in interphase. Stringent regulations govern conversion between these two states. Although the molecular mechanisms have not been fully elucidated, recent findings have begun to shed light on pathways that regulate the conversion of centrioles to basal bodies and vice versa. Emerging studies also provide insights into how defects in the balance between centrosome and cilia function could promote ciliopathies and cancer.

Can the Lewis basicity of an isolated solvent molecule be used for characterizing solvent effects?

2020 ◽  
Vol 16 ◽  
Author(s):  
Jean-François Gal ◽  
Pierre-Charles Maria
Keyword(s):  
Solvent Effects ◽  
Molecular Level ◽  
Solvent Molecule ◽  
Lewis Base ◽  
Bulk Liquid ◽  
Donor Number ◽  
Special Focus ◽  
Solution Processes ◽  
Inert Solvent

Background: The ubiquitous Lewis acid/base interactions are important in solution processes. Analytical chemistry may benefit of a better understanding of the role of Lewis basicity, at the molecular level or acting through a bulk solvent effect. Objective: To clearly delineate (i) the basicity at a molecular level, hereafter referred as solute basicity, and (ii) the solvent basicity, which is a bulk-liquid property. Method: The literature that relates Lewis basicity scales and solvent effects is analyzed. A special focus is placed on two extensive scales, the Donor Number, DN, and the BF3 affinity scale, BF3A, which were obtained by calorimetric measurement on molecules as solutes diluted in a quasi-inert solvent, and therefore define a molecular Lewis basicity. We discuss the validity of these solute scales when regarded as solvent scales, in particular when the basicity of strongly associated liquids is discussed. Results: We demonstrate the drawbacks of confusing the Lewis basicity of a solvent molecule, isolated as solute, and that of the bulk liquid solvent itself. Conclusion: Consequently, we recommend a reasoned use of the concept of Lewis basicity taking clearly into account the specificity of the process for which a Lewis basicity effect may be invoked. In particular, the action of the Lewis base, either as an isolated entity, or as a bulk liquid, must be distinguished.

scholarly journals Sub-Inhibitory Concentrations of Ciprofloxacin Alone and Combinations with Plant-Derived Compounds against P. aeruginosa Biofilms and Their Effects on the Metabolomic Profile of P. aeruginosa Biofilms

Antibiotics ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 414
Author(s):  
Didem Kart ◽  
Tuba Reçber ◽  
Emirhan Nemutlu ◽  
Meral Sagiroglu
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Inhibitory Concentration ◽  
Molecular Level ◽  
Metabolomic Profile ◽  
Gene Expressions ◽  
New Agents ◽  
Qrt Pcr ◽  
Metabolomic Approach

Introduction: Alternative anti-biofilm agents are needed to combat Pseudomonas aeruginosa infections. The mechanisms behind these new agents also need to be revealed at a molecular level. Materials and methods: The anti-biofilm effects of 10 plant-derived compounds on P. aeruginosa biofilms were investigated using minimum biofilm eradication concentration (MBEC) and virulence assays. The effects of ciprofloxacin and compound combinations on P. aeruginosa in mono and triple biofilms were compared. A metabolomic approach and qRT-PCR were applied to the biofilms treated with ciprofloxacin in combination with baicalein, esculin hydrate, curcumin, and cinnamaldehyde at sub-minimal biofilm inhibitory concentration (MBIC) concentrations to highlight the specific metabolic shifts between the biofilms and to determine the quorum sensing gene expressions, respectively. Results: The combinations of ciprofloxacin with curcumin, baicalein, esculetin, and cinnamaldehyde showed more reduced MBICs than ciprofloxacin alone. The quorum sensing genes were downregulated in the presence of curcumin and cinnamaldehyde, while upregulated in the presence of baicalein and esculin hydrate rather than for ciprofloxacin alone. The combinations exhibited different killing effects on P. aeruginosa in mono and triple biofilms without affecting its virulence. The findings of the decreased metabolite levels related to pyrimidine and lipopolysaccharide synthesis and to down-regulated alginate and lasI expressions strongly indicate the role of multifactorial mechanisms for curcumin-mediated P. aeruginosa growth inhibition. Conclusions: The use of curcumin, baicalein, esculetin, and cinnamaldehyde with ciprofloxacin will help fight against P. aeruginosa biofilms. To the best of our knowledge, this is the first study of its kind to define the effect of plant-based compounds as possible anti-biofilm agents with low MBICs for the treatment of P. aeruginosa biofilms through metabolomic pathways.

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