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141.
The aromatic di-alanine repeat is a novel 12-amino acid-long motif constituting alternate small and large hydrophobic residues that mediate the close packing of alpha-helices. A hidden Markov model profile was constructed from the motifs initially described in Soluble N-ethyl maleimide-sensitive factor attachment proteins (SNAP), a family of soluble proteins involved in intracellular membrane fusion. Scanning different sets of protein sequences showed unambiguously that this profile defines a structural motif independent of the tetratrico peptide repeat, another widespread alpha-helical motif. In addition to SNAP, aromatic di-alanine repeats are found in selective LIM homeodomain binding proteins (SLB) and in proteins from the Pyrococcus and Archaeoglobus prokaryotes. 相似文献
142.
143.
Toneff T Mende-Mueller L Wu Y Hwang SR Bundey R Thompson LM Chesselet MF Hook V 《Journal of neurochemistry》2002,82(1):84-92
Proteolytic fragments of huntingtin (htt) in human lymphoblast cell lines from HD and control cases were compared to those in human HD striatal and cortical brain regions, by western blots with epitope-specific antibodies. HD lymphoblast cell lines were heterozygous and homozygous for the expanded CAG triplet repeat mutations, which represented adult onset and juvenile HD. Lymphoblasts contained NH(2)- and COOH-terminal htt fragments of 20-100 kDa, with many similar htt fragments in HD compared to control lymphoblast cell lines. Detection of htt fragments in a homozygous HD lymphoblast cell line demonstrated proteolysis of mutant htt. It was of interest that adult HD lymphoblasts showed a 63-64 kDa htt fragment detected by the NH(2)-domain antibody, which was not found in controls. In addition, control and HD heterozygous cells showed a common 60-61 kDa band (detected by the NH(2)-domain antibody), which was absent in homozygous HD lymphoblast cells. These results suggest that the 63-64 kDa and 60-61 kDa NH(2)-domain htt fragments may be associated with mutant and normal htt, respectively. In juvenile HD lymphoblasts, the presence of a 66-kDa, instead of the 63-64 kDa N-domain htt fragment, may be consistent with the larger polyglutamine expansion of mutant htt in the juvenile case of HD. Lymphoblasts and striatal or cortical regions from HD brains showed similarities and differences in NH(2)- and COOH-terminal htt fragments. HD striatum showed elevated levels of 50 and 45 kDa NH(2)-terminal htt fragments [detected with anti(1-17) serum] compared to controls. Cortex from HD and control brains showed similar NH(2)-terminal htt fragments of 50, 43, 40, and 20 kDa; lymphoblasts also showed NH(2)-terminal htt fragments of 50, 43, 40, and 20 kDa. In addition, a 48-kDa COOH-terminal htt band was elevated in HD striatum, which was also detected in lymphoblasts. Overall, results demonstrate that mutant and normal htt undergo extensive proteolysis in lymphoblast cell lines, with similarities and differences compared to htt fragments observed in HD striatal and cortical brain regions. These data for in vivo proteolysis of htt are consistent with the observed neurotoxicity of recombinant NH(2)-terminal mutant htt fragments expressed in transgenic mice and in transfected cell lines that may be related to the pathogenesis of HD. 相似文献
144.
Chiobanu D. Roudykh I. A. Ryabinina N. L. Grechko V. V. Kramerov D. A. Darevsky I. S. 《Molecular Biology》2002,36(2):223-231
The genetic relatedness of several bisexual and of four unisexual Lacerta saxicola complex lizards was studied, using monomer sequences of the complex-specific CLsat tandem repeats and anonymous RAPD markers. Genomes of parthenospecies were shown to include different satellite monomers. The structure of each such monomer is specific for a certain pair of bisexual species. This fact might be interpreted in favor of co-dominant inheritance of these markers in bisexual species hybridogenesis. This idea is supported by the results obtained with RAPD markers; i.e., unisexual species genomes include only the loci characteristic of certain bisexual species. At the same time, in neither case parthenospecies possess specific, autoapomorphic loci that were not present in this or that bisexual species. 相似文献
145.
Spectrin repeats are three-helix bundle structures which occur in a large number of diverse proteins, either as single copies or in tandem arrangements of multiple repeats. They can serve structural purposes, by coordination of cytoskeletal interactions with high spatial precision, as well as a 'switchboard' for interactions with multiple proteins with a more regulatory role. We describe the structure of the alpha-actinin spectrin repeats as a prototypical example, their assembly in a defined antiparallel dimer, and the interactions of spectrin repeats with multiple other proteins. The alpha-actinin rod domain shares several features common to other spectrin repeats. (1) The rod domain forms a rigid connection between two actin-binding domains positioned at the two ends of the alpha-actinin dimer. The exact distance and rigidity are important, for example, for organizing the muscle Z-line and maintaining its architecture during muscle contraction. (2) The spectrin repeats of alpha-actinin have evolved to make tight antiparallel homodimer contacts. (3) The spectrin repeats are important interaction sites for multiple structural and signalling proteins. The interactions of spectrin repeats are, however, diverse and defy any simple classification of their preferred interaction sites, which is possible for other domains (e.g. src-homology domains 3 or 2). Nevertheless, the binding properties of the repeats perform important roles in the biology of the proteins where they are found, and lead to the assembly of complex, multiprotein structures involved both in cytoskeletal architecture as well as in forming large signal transduction complexes. 相似文献
146.
Chakravarti S 《Glycoconjugate journal》2002,19(4-5):287-293
Lumican and fibromodulin are collagen-binding leucine-rich proteoglycans widely distributed in interstitial connective tissues. The phenotypes of lumican-null (Lum
–/–), Fibromodulin-null (Fmod
–/–) and compound double-null (Lum
–/–
Fmod
–/–) mice identify a broad range of tissues where these two proteoglycans have overlapping and unique roles in modulating the extracellular matrix and cellular behavior. The lumican-deficient mice have reduced corneal transparency and skin fragility. The Lum
–/–
Fmod
–/– mice are smaller than their wildtype littermates, display gait abnormality, joint laxity and age-dependent osteoarthritis. Misaligned knee patella, severe knee dysmorphogenesis and extreme tendon weakness are the likely cause for joint-laxity. Fibromodulin deficiency alone leads to significant reduction in tendon stiffness in the Lum
+/+
Fmod
–/– mice, with further loss in stiffness in a lumican gene dose-dependent way. At the level of ultrastructure, the Lum
–/– cornea, skin and tendon show irregular collagen fibril contours and increased fibril diameter. The Fmod
–/– tendon contains irregular contoured collagen fibrils, with increased frequency of small diameter fibrils. The tendons of Lum
–/–
Fmod
–/– have an abnormally high frequency of small and large diameter fibrils indicating a de-regulation of collagen fibril formation and maturation. In tissues like the tendon, where both proteoglycans are present, fibromodulin may be required early in collagen fibrillogenesis to stabilize small-diameter fibril-intermediates and lumican may be needed at a later stage, primarily to limit lateral growth of fibrils Published in 2003. 相似文献
147.
Shmueli A Cohen-Gazala O Neuman-Silberberg FS 《Biochemical and biophysical research communications》2002,291(4):732-737
The establishment of axial polarity in the Drosophila egg and embryo depends on intercellular communication between two cell types in the ovary, the germline, and the soma. The genes gurken and egfr encode two essential players of this communication pathway. Gurken protein, a TGF-alpha-like molecule, is expressed in the germline, while the EGF-receptor homolog, Egfr, is expressed in the somatic cells of the ovary. Using the yeast two-hybrid system we show here, for the first time, that Gurken protein directly binds to the extracellular domain of Egfr. This direct physical association requires the presence of an intact EGF motif within Gurken protein. Furthermore, we provide evidence that this characteristic motif may be sufficient for interaction with the receptor, at list in vitro. Our results firmly establish Gurken as the germline ligand of Drosophila Egfr. 相似文献
148.
Inhibitor of apoptosis proteins (IAPs) are a conserved class of proteins that control apoptosis in both vertebrates and invertebrates. They exert their anti-apoptotic function through inhibition of caspases, the principal executioners of apoptotic cell death. Recent advances in vertebrates and Drosophila have demonstrated that IAPs use ubiquitin conjugation to control the stability, and thus the activity, of select target proteins. The Drosophila IAP1 gene is an instructive example: it employs at least two distinct ubiquitin-dependent mechanisms of protein destruction. The apoptosis-inducing genes grim, reaper and hid modulate these mechanisms, and determine the outcome. 相似文献
149.
Silverman HS Sutton-Smith M McDermott K Heal P Leir SH Morris HR Hollingsworth MA Dell A Harris A 《Glycobiology》2003,13(4):265-277
The serine- and threonine-rich tandem repeat (TR) units that make up the characteristic feature of mucin glycoproteins are often polymorphic with substantial genetic variation in TR number. The precise effect of TR number on O-glycosylation is not fully understood, although the TR number of several mucins may be associated with apparent susceptibility to certain human diseases. To evaluate the contribution of TR number to O-glycosylation, we generated a series of chimeric mucins carrying increasing numbers of TR units from the MUC5B mucin in the context of an epitope-tagged MUC1 mucin backbone. These mucins were expressed in Caco2 colon carcinoma cell clones and purified by immunoprecipitation. O-Glycosylation was investigated by western blotting with antibodies to known carbohydrate structures and by fast atom bombardment-mass spectrometry. Additional carbohydrate epitopes were detected with antibodies on chimeric mucins with a higher TR number in comparison to those with fewer TRs. Using mass spectrometry, higher-molecular-weight glycans were detected more frequently on the mucins with extended TRs compared to those with fewer TRs. However no novel carbohydrate structures were seen, suggesting that TR number does not affect the specificity of O-glycosylation. 相似文献
150.