Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The main heat shock cognate protein (hsc) of 70 kDa in Drosophila, hsc 4, was localized in cultured cells using a specific affinity-purified antibody and colloidal gold immunoelectron microscopy. This constitutively expressed member of the heat shock protein (hsp) 70 family is found in the cytosol, in mitochondria, and in the nucleus of unstressed cells. The identity of hsc 4 in these three cellular compartments was confirmed by two-dimensional gel immunoblots and partial proteolytic digestion patterns. In mitochondria, the colloidal gold particles are observed in close proximity to or on the inner membranes. The intramitochondrial localization of this hsc was confirmed by density gradient purification and by resistance of hsc 4 to externally added trypsin. In the nucleus, the labeling is found on nucleo-plasmic perichromatin RNP fibrils and is not detected in the nucleolus. Heat shock induces an intracellular redistribution of hsc 4 with an enrichment in the nucleus. The localization of this hsc in different cellular compartments is consistent with the previously suggested functions of some members of this family of proteins in basic cellular processes such as protein folding. Moreover, the present data suggests that the main constitutively expressed member of the hsp 70 family, hsc 4, functions both within the mitochondrial compartment and in the nucleus.
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PMID:Intramitochondrial localization of the main 70-kDa heat-shock cognate protein in Drosophila cells. 834 82

Heterogeneous nuclear RNP protein A1, one of the major proteins in hnRNP particle (precursor for mRNA), is known to be posttranslationally arginine-methylated in vivo on residues 193, 205, 217 and 224 within the RGG box, the motif postulated to be an RNA binding domain. Possible effect of NG-arginine methyl-modification in the interaction of protein A1 to nucleic acid was investigated. The recombinant hnRNP protein A1 was in vitro methylated by the purified nuclear protein/histone-specific protein methylase I (S-adenosylmethionine:protein-arginine N-methyltransferase) stoichiometrically and the relative binding affinity of the methylated and the unmethylated protein A1 to nucleic acid was compared: Differences in their binding properties to ssDNA-cellulose, pI values and trypsin sensitivities in the presence and absence of MS2-RNA all indicate that the binding property of hnRNP protein A1 to single-stranded nucleic acid has been significantly reduced subsequent to the methylation. These results suggest that posttranslational methyl group insertion to the arginine residue reduces protein-RNA interaction, perhaps due to interference of H-bonding between guanidino nitrogen arginine and phosphate RNA.
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PMID:Recent advances in protein methylation: enzymatic methylation of nucleic acid binding proteins. 989 55

Antigenic cross-reactivity, i.e., the capacity of a single antibody to react with apparently dissimilar structures, is a common characteristic of autoantibodies produced during systemic lupus erythematosus (SLE), an autoimmune disease developed by humans and certain strains of mice. Characterization of the extent of cross-reactivity of SLE-related autoantibodies may help identify the immunogenic stimulus, or stimuli, of autoantibody-secreting B-lymphocytes. Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) was combined with mass spectrometry (MS) to identify cell proteins recognized by a single monoclonal autoantibody (mAb 4B7), derived from an (NZW x BXSB)F1 mouse and selected based on its capacity to react with cardiolipin, that binds to elements in the cytoplasm and nucleoli of HEp-2 cells as assessed by indirect immunofluorescence assay. Proteins from HL-60 extract were separated by 1-D and 2-D PAGE. Western blotting with mAb 4B7 after SDS-PAGE revealed four bands, two intensely labeled at 35 and 32 kDa, and two weaker ones at 20 and 60 kDa; three spots were detected after 2-D PAGE. After trypsin in-gel digestion of the three protein spots, MS yielded representative matrix assisted laser desorption/ionization-time of flight (MALDI-TOF) Reflector or quadrupole-time of flight (Q-TOF) spectra. The three corresponding proteins were identified as the nucleolar phosphoprotein B23 (nucleophosmin), heterogeneous nuclear ribonucleoprotein A2 (hnRNP A2) and the 60 kDa Ro/SS-A RNP. Thus, these results showed that 2-D PAGE combined with MS constitutes a sensitive and powerful technique to characterize the full extent of cross-reactivity of a single mAb and may constitute a new approach to further characterize the immunogenic cellular components involved in the breakage of B-cell tolerance observed in SLE.
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PMID:Two-dimensional electrophoresis and mass spectrometry identification of proteins bound by a murine monoclonal anti-cardiolipin antibody: a powerful technique to characterize the cross-reactivity of a single autoantibody. 1093 68

Low mobility group nonhistone protein, LMG(160), is a ribonucleoprotein particle of the nuclear matrix with an inhibitory effect on transcription. Through the current study, we have investigated comparatively the effect and behavior of the protein in the absence and presence of its RNA moiety. Analysis was performed with the intact LMG(160) and its RNase-treated form using native and denatured gel electrophoresis as well as fluorescence spectroscopy and trypsin digestion techniques. The results show that the RNA moiety of LMG(160) plays a key role in maintaining the overall structure and conformation of this RNP particle, in the way that RNA removal causes some alterations in the structural stability of the protein, leading it to become self-associated. This finding can easily explain the loss of function of LMG(160) after RNase-treatment, the effect that may influence the biological activity of the molecule in the nuclear matrix structure.
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PMID:Evidence for the structural stability of ribonucleoprotein LMG(160) under ribonuclease-A treatment. 1875 75


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