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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 57 (2000), S. 899-913 
    ISSN: 1420-9071
    Schlagwort(e): Key words. Small heat shock/α-crystallin protein; oligomer formation; protein folding; molecular chaperone.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Small heat shock/α-crystallin proteins are defined by a conserved sequence of approximately 90 amino acid residues, termed the α-crystallin domain, which is bounded by variable amino- and carboxy-terminal extensions. These proteins form oligomers, most of uncertain quaternary structure, and oligomerization is prerequisite to their function as molecular chaperones. Sequence modelling and physical analyses show that the secondary structure of small heat shock/α-crystallin proteins is predominately β-pleated sheet. Crystallography, site-directed spin-labelling and yeast two-hybrid selection demonstrate regions of secondary structure within the α-crystallin domain that interact during oligomer assembly, a process also dependent on the amino terminus. Oligomers are dynamic, exhibiting subunit exchange and organizational plasticity, perhaps leading to functional diversity. Exposure of hydrophobic residues by structural modification facilitates chaperoning, where denaturing proteins in the molten globule state associate with oligomers. The flexible carboxy-terminal extension contributes to chaperone activity by enhancing the solubility of small heat shock/α-crystallin proteins. Site-directed mutagenesis has yielded proteins where the effect of the change on structure and function depends upon the residue modified, the organism under study and the analytical techniques used. Most revealing, substitution of a conserved arginine residue within the α-crystallin domain has a major impact on quaternary structure and chaperone action, probably through realignment of β-sheets. These mutations are linked to inherited diseases. Oligomer size is regulated by a stress-responsive cascade including MAPKAP kinase 2/3 and p38. Phosphorylation of small heat shock/α-crystallin proteins has important consequences within stressed cells, especially for microfilaments.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Marine biology 107 (1990), S. 93-102 
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We describe the effect of inorganic mercury on the emergence, hatching and growth ofArtemia franciscana (commercially obtained). At concentrations as low as 0.01µmol 1−1, mercury delays development of the organism, but the effect on the final number of developed brine shrimp is small. At higher concentrations, mercury has a dramatic effect, inhibiting the developmental process at the emergence and hatching stages. As recorded by light and scanning electron microscopy, organisms stalled at emergence are not immediately killed. Their eye spots continue to darken and some may hatch although partially enclosed in the cyst shell. Completely emerged prenauplii in the presence of mercury often have an abnormal oval shape while hatched organisms may display shortened and deformed bodies and exhibit restricted movement. The results demonstrate that emergingA. franciscana are very sensitive to inorganic mercury and the potential usefulness of this organism for the study of metal effects upon physiological processes is indicated.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 281 (1995), S. 507-515 
    ISSN: 1432-0878
    Schlagwort(e): Microtubules ; Isoforms ; Nervous system ; Locomotion ; Cilia ; Immunocytochemistry ; Western blotting ; Lymnaea stagnalis (Mollusca)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Immunocytochemistry and Western blotting techniques demonstrated that the nervous system and foot of the pond snail Lymnaea stagnalis are rich sources of tubulin, which can be extracted and assembled in vitro in the presence of taxol. Various broad-spectrum antibodies raised against α-tubulin and β-tubulin yielded qualitatively similar results. One monoclonal antibody to trypanosome α-tubulin, however, labelled α-tubulin more strongly on both probed sections and Western blots. Cytochemistry and immunoblotting revealed that tyrosinated tubulin constitutes a large proportion of total α-tubulin in locomotor cilia of the foot and in axons of the nervous system. Detyrosinated tubulin also appeared to be abundant in the foot cilia but only a very faint band of detyrosinated tubulin was found on protein blots extracted from the central ganglia, and staining was barely detectable in central ganglia or peripheral nerves. Similarly, acetylated tubulin appeared to be abundant in foot cilia, but Western blotting indicated only low levels of acetylated tubulin in the nervous system. Immunocytochemistry indicated that, while most neurons possessed little or no acetylated tubulin, a small number of axons contained significant amounts of this isoform. Thus, while a large amount of tubulin was expected in the nervous system and locomotor cilia of L. stagnalis, the observed distribution of isoforms was unanticipated. Specifically, neurons of other organisms have generally been reported to contain substantial amounts of both detyrosinated α-tubulin and acetylated α-tubulin. Our results indicate that such findings cannot be generalized across all species. L. stagnalis, with its well studied nervous system and unusual distribution of tubulin isoforms, may prove to be particularly useful for studying the roles of tubulin isoforms in microtubule function and cell activity.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 281 (1995), S. 507-515 
    ISSN: 1432-0878
    Schlagwort(e): Key words: Microtubules ; Isoforms ; Nervous system ; Locomotion ; Cilia ; Immunocytochemistry ; Western blotting ; Lymnaea stagnalis (Mollusca)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Immunocytochemistry and Western blotting techniques demonstrated that the nervous system and foot of the pond snail Lymnaea stagnalis are rich sources of tubulin, which can be extracted and assembled in vi- tro in the presence of taxol. Various broad-spectrum antibodies raised against α-tubulin and β-tubulin yielded qualitatively similar results. One monoclonal antibody to trypanosome α−tubulin, however, labelled α-tubulin more strongly on both probed sections and Western blots. Cytochemistry and immunoblotting revealed that tyrosinated tubulin constitutes a large proportion of total α-tubulin in locomotor cilia of the foot and in axons of the nervous system. Detyrosinated tubulin also appeared to be abundant in the foot cilia but only a very faint band of detyrosinated tubulin was found on protein blots extracted from the central ganglia, and staining was barely detectable in central ganglia or peripheral nerves. Similarly, acetylated tubulin appeared to be abundant in foot cilia, but Western blotting indicated only low levels of acetylated tubulin in the nervous system. Immunocytochemistry indicated that, while most neurons possessed little or no acetylated tubulin, a small number of axons contained significant amounts of this isoform. Thus, while a large amount of tubulin was expected in the nervous system and locomotor cilia of L. stagnalis, the observed distribution of isoforms was unanticipated. Specifically, neurons of other organisms have generally been reported to contain substantial amounts of both detyrosinated α-tubulin and acetylated α-tubulin. Our results indicate that such findings cannot be generalized across all species. L. stagnalis, with its well studied nervous system and unusual distribution of tubulin isoforms, may prove to be particularly useful for studying the roles of tubulin isoforms in microtubule function and cell activity.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 210 (1999), S. 92-98 
    ISSN: 1615-6102
    Schlagwort(e): Posttranslational modification ; Tubulin ; Tyrosination ; Conifer ; Angiosperm
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The distribution of tyrosinated and detyrosinated tubulin in microtubule arrays of pine and onion cells was investigated by immunofluorescence techniques. Staining of isolated cells and methacrylate sections ofPinus radiata andAllium cepa root tips indicated that all microtubule structures contained tyrosinated tubulin but not the posttranslationally modified detyrosinated tubulin. The detyrosinated tubulin epitope was, however, created in vitro by treating both sections and fixed whole cells with carboxypeptidase A.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 207 (1999), S. 174-185 
    ISSN: 1615-6102
    Schlagwort(e): Posttranslational modification ; Tubulin ; Acetylation ; Monoclonal antibody 6-11B-1 ; Gymnosperm ; Angiosperm
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The distribution of acetylated tubulin in microtubule arrays of conifer cells was investigated by immunofluorescence techniques with 6-11B-1, a monoclonal antibody specific for posttranslationally acetylated α-tubulins. In methacrylate sections ofPinus radiata andPinus conforta root tip cells, acetylated tubulin was detected in mitotic spindles, phragmoplasts, and cortical microtubules. Furthermore, staining of isolated, intact cells ofP. radiata andP. contorta indicated that all microtubule structures, including preprophase bands, prophase, metaphase and anaphase spindles, and phragmoplasts, contained some acetylated tubulin, and that the intensity of staining with 6-11B-1 was variable. For example, preprophase bands were lightly labelled, kinetochore fibres of anaphase spindles and phragmoplasts were heavily stained, and metaphase spindles had a granular appearance suggesting discontinuous acetylation of their constituent microtubules. This first report of the presence of acetylated tubulin in conifer cells is in contrast to our results with two species of angiosperms where no acetylated tubulin was detected. The significance of this and the variability of the intensity of staining in conifer arrays is discussed in terms of microtubule dynamics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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