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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Antibodies to synthetic peptides from the alpha and beta-tubulin sequences were employed to study zones of this protein active in microtubule assembly. In purified calf brain tubulin, six short sequences, selected according to their hydrophilicity and conservation, were found to be accessible to their affinity-purified immunoglobulin G (IgG) antibodies, in a competition radioimmunoassay performed under non-assembly native conditions. This indicated that the six sequences are exposed on the surface of the tubulin alpha beta heterodimer. IgG antibodies to the alpha(430-443) and beta(412-431) sequences perturbed substoichiometrically the assembly of purified tubulin, inducing microtubule bundling and the formation of opened up structures. These positions, which are close to the C termini, were accessible to the anti-peptide antibodies in taxol-induced microtubules, Zn2(+)-induced tubulin sheets, Mg2(+)-induced tubulin rings and in PtK2 cell microtubules. This, together with the comparison of the sizes and gross shapes of the antibody probes and microtubules, suggested that these sequences might be located at the protruding parts of the protofilaments. Antibodies to positions alpha(155-168) did not react with microtubules, while the equivalent zone beta(153-165) was accessible. The alpha(214-226) and beta(241-256) sequences were antigenically occluded in the taxol microtubules, Zn2(+)-induced sheets and Mg2(+)-induced ring arrays, as well as in native microtubules from PtK2 cells, though they became reactive by fixation. This result strongly suggested that these two zones are close to tubulin-tubulin contact sites. A working model is proposed in which the positions alpha(214-226) and beta(241-256) are close to the axial contacts between heterodimers, which lead to protofilament formation, while the positions alpha(241-256) and beta(214-226) are suggested to be related to the alpha-beta binding interface within the heterodimer.
J Mol Biol 1990 Jul 05
PMID:Tubulin assembly probed with antibodies to synthetic peptides. 169 48

We examined the developmental expression of a diverged soybean beta-tubulin gene (designated sb-1), which had been cloned and sequenced previously. A probe specific for the sb-1 gene was constructed from the 3' transcribed untranslated sequence. As a control, a more general probe for beta-tubulin genes and their transcripts was constructed from a highly conserved region of the third exon of another soybean beta-tubulin gene, sb-2. Poly(A)+ RNA, extracted from various soybean tissues and organs, was probed alternatively with the sb-1 gene-specific probe and with the generic beta-tubulin probe. Levels of beta-tubulin transcripts recognized by the generic probe differed by a factor of approximately 3 in the different tissues and organs and varied with the state of organ development. Highest levels were found in young, unexpanded leaves and they decreased as leaf maturation occurred. In contrast, transcripts of sb-1 were nearly undetectable in young leaves, and they increased as leaf maturation occurred. Levels of sb-1 transcript were low in all organs of the light-grown plant examined, except the hypocotyl, where they were approximately 10-fold higher. However, the highest levels of sb-1 transcripts were observed in elongating hypocotyls of etiolated seedlings. Exposure of six-day-old etiolated seedlings to light for 12 hours halted further hypocotyl elongation and brought about a dramatic, nearly 100-fold, decrease in the steady-state level of sb-1 transcripts.
Plant Mol Biol 1991 Feb
PMID:Limited expression of a diverged beta-tubulin gene during soybean (Glycine max [L.] Merr.) development. 171 97

Tubulin synthesis is controlled by an autoregulatory mechanism through which an increase in the intracellular concentration of tubulin subunits leads to specific degradation of tubulin mRNAs. The sequence necessary and sufficient for the selective degradation of a beta-tubulin mRNA in response to changes in the level of free tubulin subunits resides within the first 13 translated nucleotides that encode the amino-terminal sequence of beta-tubulin, Met-Arg-Glu-Ile (MREI). Previous results have suggested that the sequence responsible for autoregulation resides in the nascent peptide rather than in the mRNA per se, raising the possibility that the regulation of the stability of tubulin mRNA is mediated through binding of tubulin or some other cellular factor to the nascent amino-terminal tubulin peptide. We now show that this putative cotranslational interaction is not mediated by tubulin alone, as no meaningful binding is detectable between tubulin subunits and the amino-terminal beta-tubulin polypeptide. However, microinjection of a monoclonal antibody that binds to the beta-tubulin nascent peptide selectively disrupts the regulation of beta-tubulin, but not alpha-tubulin, synthesis. This finding provides direct evidence for cotranslational degradation of beta-tubulin mRNA mediated through binding of one or more cellular factors to the beta-tubulin nascent peptide.
Mol Cell Biol 1992 Feb
PMID:Physical evidence for cotranslational regulation of beta-tubulin mRNA degradation. 173 44

Insulin has rapid pleiotropic effects on cellular metabolism. In certain cell types, insulin can cause morphological changes by inducing rearrangements of cytoskeletal components, but the regulation of cytoskeletal gene expression by insulin has not been previously described. In the present work insulin was found to rapidly, but transiently, increase transcription of the cytoskeletal beta-actin and alpha-tubulin genes in rat H4IIE hepatoma cells. Insulin-induced transcription of beta-actin mRNA was evident within 5 min and was maximal by 10-15 min at 1000% above control levels. beta-Actin transcription was induced at insulin concentrations as low as 5 x 10(-12) M insulin and was maximal at 5 x 10(-9) M. Transcription of the alpha-tubulin gene was also rapidly stimulated by physiological concentrations of insulin, but only to 300-400% above basal levels. For both the beta-actin and alpha-tubulin genes, the induction of transcription was transient, with a return to basal levels by 60-120 min. Transcription of neither the skeletal or cardiac alpha-actin gene nor the beta-tubulin gene was altered by insulin administration. Messenger RNA levels for the beta-actin and alpha-tubulin genes increased, but to a lesser extent than transcription, since these mRNAs were abundant and stable before the transient induction of transcription. Inhibitors of protein synthesis, in the presence or absence of insulin, also acutely stimulated transcription of these genes.
Mol Endocrinol 1992 Jan
PMID:Induction of cytoskeletal gene expression by insulin. 173 64

We have examined the expression of beta-tubulin genes in the parasitic nematode, Brugia pahangi. A genomic library was constructed and screened by hybridization with a Haemonchus contortus beta-tubulin cDNA fragment which recognizes several B. pahangi beta-tubulin sequences, including sequences which correspond to the previously characterized beta 1-tubulin gene. The B. pahangi beta 2-tubulin gene was isolated by selecting clones which hybridize to the H. contortus beta-tubulin gene but which do not hybridize to the beta 1-tubulin gene. A partial sequence of the beta 2-tubulin gene confirms that it codes for a distinct beta-tubulin. Southern hybridization analyses show that the beta 2-tubulin sequence exists as a single copy gene within the B. pahangi genome. Expression of the beta 2-tubulin gene is developmentally regulated and the message is found predominantly in adult male worms, whereas the beta 1-tubulin gene is expressed in microfilariae and approximately equal levels of the transcript are found in male and female adult worms. During mRNA maturation the beta 1-tubulin mRNA of microfilariae and adult worms acquires a trans-spliced leader identical to the SL1 of Caenorhabditis elegans.
Mol Biochem Parasitol 1992 Feb
PMID:Identification of a novel Brugia pahangi beta-tubulin gene (beta 2) and a 22-nucleotide spliced leader sequence on beta 1-tubulin mRNA. 174 Oct 15

Experimental evidence indicates that tubulin is the site of action of the anthelmintic benzimidazoles. Furthermore, certain residues of beta-tubulin seem to be critical for this mechanism. Although the benzimidazoles selectively affect nematode vs. mammalian beta-tubulin, the molecular basis for this differential action is not known. To enhance our understanding of this phenomenon, and to provide the basis for investigating benzimidazole resistance in parasitic nematodes, we undertook the cloning of beta-tubulin cDNAs from the ruminant parasite, Haemonchus contortus. We have cloned and sequenced three beta-tubulin cDNAs from this organism, beta 12-16, beta 12-164, and beta 8-9. The first 2 differ at only 23 nucleotides, which give rise to 4 amino acid changes. beta 8-9 represents a different isotype class from the other two, since it differs extensively in the carboxyterminus. By comparing the sequences of these and other nematode beta-tubulins with mammalian beta-tubulins, several regions of consistent difference can be recognized; the functional significance of these regional differences has not been defined. Sequences very similar or identical to beta 8-9 and beta 12-16 are present in both benzimidazole-sensitive and benzimidazole-resistant populations of H. contortus. However, it appears that drug-resistant organisms may differ in the presence of a gene product which is closely related to beta 8-9.
Mol Biochem Parasitol 1992 Feb
PMID:Three beta-tubulin cDNAs from the parasitic nematode Haemonchus contortus. 174 Oct 17

Inability to culture the disease-producing amastigote form of Leishmania has greatly hampered its study. We have biochemically characterized an axenically cultured amastigote-like form of Leishmania pifanoi. This form closely resembles amastigotes in proteinase, ribonuclease, adenine deaminase and peroxidase activity. It also exhibits comparable rates of growth, transformation, synthesis of DNA, RNA and protein, and metabolism of glucose and linoleic acid. It is distinct from promastigotes in these characteristics. The expression of the genes for beta-tubulin and the P100/11E reductase is developmentally regulated in this axenic form as in amastigotes. These results, combined with previous demonstrations of amastigote morphology and antigenicity in the culture form, confirm that Leishmania amastigotes have been successfully propagated in axenic media. This strain should serve as an excellent model for the study of amastigote biochemistry, pharmacology and immunology, and the molecular genetics of the transformation between amastigote and promastigote forms.
Mol Biochem Parasitol 1991 Nov
PMID:Biochemical and molecular characterization of Leishmania pifanoi amastigotes in continuous axenic culture. 177 52

The molecular karyotypes of several Leishmania isolates (Leishmania amazonensis, Leishmania braziliensis, Leishmania guyanensis, Leishmania panamensis, Leishmania donovani, Leishmania major, Leishmania aethiopica, Leishmania tropica, Leishmania enriettii) have been analyzed by clamped homogeneous electric field (CHEF) gel electrophoresis. The chromosomal localization of genes encoding 2 major surface glycoproteins, gp63 and gp46/M2, heat shock protein 70 (hsp70), and beta-tubulin was determined for cloned isolates of 8 of these Leishmania species. The chromosome size class assignment of hsp70 genes was most conserved in that all species contained a single hybridizing DNA band of approximately 1200 kb. The beta-tubulin gene probe hybridized predominantly to large (1600-1750 kb) chromosome-size DNA and to 1-5 additional bands, the number of which depended on the species. The number and size of DNA bands hybridizing to gp63 or gp46/M2 gene probes were not uniformly conserved among species. In contrast to previous reports of gp63 genes being located on a single chromosome, using various CHEF gel conditions we observed a Leishmania major gp63 gene probe hybridizing to at least 2 chromosomal DNA bands in the New World species and in L. tropica. Gp46/M2 genes were located on 1 band in L. donovani, L. major, and L. aethiopica or 2 bands in L. tropica and L. amazonensis, but surprisingly, do not hybridize to any chromosomal DNA of species in the L. braziliensis complex or in L. enriettii. Whenever both genes were present in a species, gp63 and gp46/M2 genes were located on different chromosomal DNA bands.
Mol Biochem Parasitol 1991 Sep
PMID:Molecular karyotype and chromosomal localization of genes encoding two major surface glycoproteins, gp63 and gp46/M2, hsp70, and beta-tubulin in cloned strains of several Leishmania species. 177 88

The beta-tubulin genes G beta 1 and G beta 2 from the phytopathogenic hemiascomycete Geotrichum candidum were found to be highly diverged in amino acid sequence from those of other filamentous fungi. G beta 1 and G beta 2 were also divergent from each other, with the coding regions sharing only 66% nucleotide sequence homology and 64% amino acid identity. However, the proteins shared 82% similarity and only 25 of the 161 non-identical amino acid substitutions were non-conservative. The organization of G beta 1 is similar to other fungal beta-tubulin genes, but G beta 2 has several unusual features; it has 2 amino acid additions in the N-terminal 40 residues and must employ an uncommon 5' splice junction sequence in preference to an overlapping perfect consensus. The amino acid change found to confer benomyl resistance in Neurospora crassa was also present in G beta 2. G beta 1 has four introns which are located similarly to those of beta-tubulin genes in other fungi. G beta 2, however, has a single intron in a unique location. Translational fusions employing the 5' non-coding regions of the two Geotrichum beta-tubulin genes were made with the hygromycin phosphotransferase gene and shown to function in Schizosaccharomyces pombe and Trichoderma hamatum. However, G. candidum could not be transformed with these or other tested plasmids commonly used for fungal transformation.
Mol Gen Genet 1991 Nov
PMID:Characterization of two beta-tubulin genes from Geotrichum candidum. 183 49

We have compared benzimidazole (BZ) susceptible (s) and resistant (R) strains of Haemonchus contortus from sheep by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE), Western blotting and ELISA techniques. The S strain bound more drug per mg protein than the R strain. BZ binding could be resolved into high-affinity and low-affinity binding. Low-affinity binding in parasite preparations devoid of tubulin was observed, but high-affinity binding occurred only in preparations containing tubulin. Resistance was associated with a decrease in the high affinity component. The S and R strains were shown by ELISA to contain similar total amounts of tubulin. By 2-D PAGE, the beta-tubulin isoform pattern of the S strain was different from that of the R strain, but the alpha-tubulin isoform patterns of the 2 strains were similar. BZ resistance was associated with a decrease in high-affinity BZ binding to tubulin and an alteration in beta-tubulin isoform pattern.
Mol Biochem Parasitol 1991 Jul
PMID:Beta-tubulin and benzimidazole resistance in the sheep nematode Haemonchus contortus. 185 82


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