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

Trypanosoma brucei brucei, a protozoan parasite of wild and domestic animals in Africa, is related to the pathogenic agent of human sleeping sickness. Four H1 histone proteins were isolated from nuclei of procyclic culture forms and cleaved with proteases. Amino acid sequence analysis of purified fragments indicated the presence of variants which displayed sequence identities as compared to the C-terminal domain of human H1. Substitutions of amino acids and posttranslational modifications of the histones in T b brucei H1 may influence protein conformation and histone-histone as well as histone-DNA interactions in the chromatin of the parasite. Digestion of soluble chromatin with immobilized trypsin at low and high ionic strengths indicated an internal localization of H1 in the condensed chromatin. The influence of histone H1 of T b brucei on the compaction pattern of the chromatin was investigated by dissociation and reconstitution experiments. Electron microscopy revealed that trypanosome H1 was able to induce condensation of the chromatin of the parasite and of rat liver into dense tangles. After dephosphorylation of H1, 30 nm fibers were induced in rat liver chromatin, while the resulting fibers were distinctly thinner in T b brucei. It can be concluded that the absence of 30 nm fibers in T b brucei chromatin cannot be explained by the divergent variants and posttranslational phosphorylations of H1 only but rather by the influence of both, the divergent core histones, previously described, and H1 properties.
 ...
PMID:Partial amino acid sequence and functional aspects of histone H1 proteins in Trypanosoma brucei brucei. 764 5

The sensitive electric-birefringence method was used to reveal structural differences between the soluble chromatin of procyclic Trypanosoma brucei brucei and the chromatin of the higher eukaryotes. The orientation of the nucleosomal chains and the presence of extended DNA were analysed from the sign and amplitude of the steady-state birefringence, and the conformational properties (overall dimensions and flexibility) were studied in relation to the orientational relaxation times. In contrast to the higher eukaryotes, the birefringence of T. brucei brucei is negative and of low amplitude, corresponding to that of H1-depleted rat liver nucleosomes. Furthermore, the relaxation times are very small, about 10 microseconds. If salt is added, the birefringence as well as the relaxation time decreases dramatically, indicating that condensation affects T. brucei brucei chromatin although it behaves like nucleosome filaments, with less stable DNA-protein interaction than for the higher eukaryotes. However, this condensation does not induce the formation of regular higher-order structure. This complies with the hypothesis that typical histone H1 is absent from T. brucei brucei chromatin and that a protein or protein domain fulfils the role of histone H1. The accessibility and structural role of histone-like proteins in T. brucei brucei chromatin were also investigated using limited proteolysis with enzymes covalently bound to nylon spheres. The analysis of protein products obtained after digestion with immobilized trypsin and subtilisin shows that proteins a and d, which are classified as H3 and H4 histones, respectively, are the first to be attacked. The changes in chromatin conformation indicate that chromatin undergoes a structural transition, leading to decondensation, as indicated by increases in negative birefringence and relaxation time, and to a change in its orientation mechanism, indicated by the appearance of a permanent moment. This result is very interesting since, in rat liver, H4 was very resistant and was the last histone to be attacked, suggesting internal location and its involvement in nucleosome stabilization rather than higher-order condensation. Therefore, in T. brucei brucei chromatin, the characteristic properties of proteins a and d (their composition and interaction with DNA), as well as their external location on the nucleosome surface, suggest that if these proteins play a role similar to that played by H3 and H4 in higher eukaryotes, probably through their N-terminal regions and interaction either with DNA or protein domains, the mechanisms involved in chromatin compaction are quite different.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Structural analysis of Trypanosoma brucei brucei chromatin by limited proteolysis. An electrical-birefringence study. 837 78

The location of linker histones H1 and H5 in chicken erythrocyte chromatin was studied as a function of the fiber structure by the use of proteolytic enzymes immobilized onto Immobilon membranes. The immobilization of trypsin and chymotrypsin creates proteolytic probes, specific respectively to the terminal portions of the molecules or to the phenylalanine in the globular domain, that are incapable of penetrating into the interior of the condensed fiber. The chromatin fiber was studied in three different conformations: open zig-zag (in Tris buffer), closed zig-zag (upon addition of 10 mM-NaCl), or 30 nm fiber (upon addition of 0.35 mM-MgCl2). The results from digestion experiments performed on linker histones either in chicken erythrocyte chromatin, or free in solution or bound in mononucleosomes revealed several features relevant to linker histone location: (1) histone H5 is more protected than histone H1 in the fiber; (2) the N and C-terminal portions of histone H1 do not change their accessibility, and hence their location, upon compaction of the fiber; this behavior of H1 is in contrast to that of histone H5, whose tails become significantly internalized in the 30 nm fiber; (3) phenylalanine in the globular domain of both H1 and H5 is inaccessible (buried) both in the fiber and in the mononucleosomal particle. Sedimentation velocity measurements performed during the course of trypsin digestion demonstrate that the conformation of the fiber is highly sensitive to even a few cuts in some of the linker histone molecules; hence, the linker histones are an important factor in the organization of the fiber in all its different condensation states.
 ...
PMID:On the location of histones H1 and H5 in the chromatin fiber. Studies with immobilized trypsin and chymotrypsin. 844 56

Amino acid analyses of nuclear basic proteins of an anuran amphibian, Rana catesbeiana, revealed that they are comprised of a full set of core histones and three types of lysine-rich, sperm-specific proteins. On the basis of their amino-acid compositions and partial amino-acid sequences of their trypsin-resistant cores, the sperm-specific proteins could be defined as members of the histone H1 family. Both micrococcal nuclease digestion and electron microscopy indicated that sperm chromatin consists of nucleosomal and fibrillar DNA structures which are irregularly interspersed with each other. When sperm nuclei were incubated with nucleoplasmin, nuclei decondensed to some extent, and the sperm-specific H1s were removed, but not completely. The residual sperm-specific histone H1 variants were also found in reconstituted male pronuclear chromatin, comprising regularly spaced nucleosomes. We conclude that sperm-specific histone H1 variants are essential for chromatin condensation in the sperm nuclei, but that their complete removal is not necessary for the remodeling into somatic chromatin that takes place after fertilization.
 ...
PMID:Histone H1 variants as sperm-specific nuclear proteins of Rana catesbeiana, and their role in maintaining a unique condensed state of sperm chromatin. 913 20

We have determined the presence of cysteine in the protein PL-I from the sperm of the surf clam Spisula solidissima. The existence of cysteine in this histone H1-related protein is responsible for its previously described aggregation behavior. The location of this residue, within the trypsin-resistant domain of the protein, has been established. We have also shown that cysteine is ubiquitously present in the PL-I proteins from the sperm of other bivalve mollusks but is absent from other PL of smaller molecular mass (PL-II, PL-III, PL-IV). We have also found cysteine to be present in the PL-I from a tunicate (Chelysoma productum) but absent in a PL-I from a fish (Mullus barbatus). The possible significance of the unusual occurrence of cysteine in these histone-H1-related proteins is discussed.
 ...
PMID:Cysteine-containing histone H1-like (PL-I) proteins of sperm. 1054 81

pANCA is a marker antibody expressed in most patients with ulcerative colitis, and its cognate antigen is potentially an immunologic target in this disease. This study evaluates whether pANCA detects an autoantigen that is expressed in the colonic mucosa. Immunohistochemistry of colon specimens with human pANCA monoclonal antibodies (Fab 5-2 and 5-3) revealed a minor population of immunoreactive mucosal cells bearing a cytoplasmic vesicle antigen. By distribution, morphology, and tryptase expression, these were identified as mast cells. Immunofluorescent analysis revealed similar immunoreactivity of mouse mast cell lines and human KU812. Western analysis of mouse mast cell lines revealed immunoreactive proteins, and these were distinct from previously proposed pANCA antigens (histone H1, HMG 1 and 2, and neutrophil vesicle antigens). Cognate antigen for Fab 5-2 and 5-3 was also expressed in other tissue mast cells, cerebellar neurons, and pancreatic islet cells. These findings identify a novel cytoplasmic autoantigen(s) associated with UC by its presence in colonic mucosa and recognition by a disease-associated marker antibody.
 ...
PMID:Mast cell and neuroendocrine cytoplasmic autoantigen(s) detected by monoclonal pANCA antibodies. 1060 89

The cytotoxic T lymphocyte protease granzyme A induces caspase-independent cell death in which DNA single-strand nicking is observed instead of oligonucleosomal fragmentation. Granzyme A is a specific tryptase that concentrates in the nucleus of targeted cells and synergistically enhances DNA fragmentation induced by the caspase activator granzyme B. Here we show that granzyme A treatment of isolated nuclei enhances DNA accessibility to exogenous endonucleases. In vitro and after cell loading with perforin, GrnA completely degrades histone H1 and cleaves core histones into approximately 16-kDa fragments. Histone digestion provides a mechanism for unfolding compacted chromatin and facilitating endogenous DNase access to DNA during T cell and natural killer cell granule-mediated apoptosis.
 ...
PMID:Induction of rapid histone degradation by the cytotoxic T lymphocyte protease Granzyme A. 1106 Feb 86

The contribution of the linker region to maintenance of condensed chromatin was examined in two model systems, namely sea urchin sperm nuclei and chicken red blood cell nuclei. Linkerless nuclei, prepared by extensive digestion with micrococcal nuclease, were compared with Native nuclei using several assays, including microscopic appearance, nuclear turbidity, salt stability, and trypsin resistance. Chromatin in the Linkerless nuclei was highly condensed, resembling pyknotic chromatin in apoptotic cells. Linkerless nuclei were more stable in low ionic strength buffers and more resistant to trypsin than Native nuclei. Analysis of histones from the trypsinized nuclei by polyacrylamide gel electrophoresis showed that specific histone H1, H2B, and H3 tail regions stabilized linker DNA in condensed nuclei. Thermal denaturation of soluble chromatin preparations from differentially trypsinized sperm nuclei demonstrated that the N-terminal regions of histones Sp H1, Sp H2B, and H3 bind tightly to linker DNA, causing it to denature at a high temperature. We conclude that linker DNA exerts a disruptive force on condensed chromatin structure which is counteracted by binding of specific histone tail regions to the linker DNA. The inherent instability of the linker region may be significant in all eukaryotic chromatins and may promote gene activation in living cells.
 ...
PMID:Linker DNA destabilizes condensed chromatin. 1146 48

Extraction of sperm proteins from the bivalve mollusc Ostrea edulis shows them to contain a normal complement of core histones, together with three sperm-specific proteins, OE1 and OE2, plus the shorter OE3, which shows substantial microheterogeneity. OE1 and OE2 have a very similar amino acid composition, cyanogen bromide (CNBr) cleavage yields products of identical size and possesses a trypsin-resistant core peptide, together indicating that they are closely homologous histone H1-like proteins. Western blotting shows that OE1 and OE2 are closely related to the histone H1-like protein PL-II* of Mytilus trossulus. The amino acid composition of OE3 shows it to be a protamine-like PL-IV type protein. Edman degradation of a CNBr peptide from OE2 gave the sequence (M)KAAFAKGLKSGALVRPKGS-which has 85% identity to a sequence located towards the C-terminal end of the globular domain of the PL-II* protein of M. trossulus. An O. edulis sperm cDNA library yielded a clone of 428 bp. A genomic clone including an open reading frame (ORF) of 750 bp was isolated by PCR amplification from genomic DNA. Hypothetical translation showed the ORF to encode OE1 (or OE2) immediately followed by OE3, separated by a proteolytic processing site. This arrangement (a two-protein ORF) is also found in M. trossulus and Ensis minor.
 ...
PMID:The sperm-specific proteins of the edible oyster (European flat oyster (Ostrea edulis)) are products of proteolytic processing. 1473 86

Daunomycin is an anticancer drug that is well-known to interact with DNA in chromatin. Using a compositionally defined chicken erythrocyte chromatin fraction, we have obtained conclusive evidence that the drug is also able to interact with chromatin-bound linker histones without any noticeable binding to core histones. The drug can interact in an equal fashion with both histone H1 and H5 and to a greater extent with core histones H3/H4 and H2A/H2B as free proteins in solution. Thus, the binding of daunomycin to linker histones in the chromatin fiber is most likely due to the well-known higher accessibility of these histones to the surrounding environment of the fiber. Binding of daunomycin to linker histones appears to primarily involve the trypsin-resistant (winged-helix) domain of these proteins. The studies described here reveal the occurrence of a previously undisclosed mechanism for the antitumor activity of anthracycline drugs at the chromatin level.
 ...
PMID:Binding of antitumor antibiotic daunomycin to histones in chromatin and in solution. 1561 44


<< Previous 1 2 3 4 5 6 Next >>