Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.17 (lysozyme)
 21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The structures of the choline-dependent pneumococcal murein hydrolases, LYTA amidase and CPL1 lysozyme, and the choline-independent CPL7 lysozyme were analysed by controlled proteolytic digestions. The trypsin cleavage of the CPL1 and CPL7 lysozymes produced two resistant polypeptides, F1 and F7 respectively, corresponding to the N-terminal domain of the enzymes, whereas the amidase LYTA was completely hydrolysed by the protease. Interestingly, the F1 and F7 fragments showed a low, but significant, choline-independent lysozyme activity. Choline reduced the rate of proteolytic hydrolysis of choline-dependent enzymes, suggesting that the C-terminal choline-binding domain adopts a more resistant conformation in the presence of the ligand. On the other hand, the regions encoding the N-terminal domains of the three enzymes have been cloned and expressed in Escherichia coli, showing that these domains adopt an active conformation even in the absence of their C-terminal domains. The lower activity shown by the catalytic domains when compared with that of the complete enzymes suggests that the acquisition of a substrate-binding domain represents a noticeable evolutionary advantage for enzymes that interact with polymeric substrates, allowing them to achieve a higher catalytic efficiency. These results strongly reinforce the hypothesis that the pneumococcal murein hydrolases have been originated by fusion of two structural and functional independent domains, and provide new experimental support to the theory of modular evolution of proteins.
Mol Microbiol 1992 Apr
PMID:Studies on the structure and function of the N-terminal domain of the pneumococcal murein hydrolases. 135 Dec 40

Monocytic leukemia (MoL) cells were obtained from the peripheral blood of a patient in whom the leukemic cells infiltrating various lymphoreticular organs exhibited features intermediate between interdigitating reticulum cells (IDC) and ordinary phagocytic macrophages, whereas the leukemic cells in the peripheral blood were essentially monocytic and lacked such features. Peripheral blood CD4+ T-cells were established as an interleukin-2-dependent T-cell line. When the MoL cells were exposed for a few days to conditioned medium from the T-cell line, they extended several dendritic cytoplasmic projections and became intensely positive for HLA-DR antigen, cytoplasmic S-100 beta protein, and CD1 antigen. Functionally, the conditioned medium significantly down-regulated Fc-mediated and Fc-independent phagocytic activities, and the levels of lysosomal enzymes such as lysozyme and nonspecific esterase in the MoL cells. Moreover, the conditioned medium significantly up-regulated the accessory cell function of the MoL cells as measured by the primary allogenic mixed leukocyte reaction (MLR). Furthermore, the conditioned medium significantly down-regulated the expression of CD14 antigen. Biochemical analysis indicated that the factor responsible for these changes is a protein which is distinct from known human cytokines and whose molecular weight is approximately 31 kDa. These findings suggest that IDC are closely related the monocytic lineage and that helper T-cells play an important role in constructing the microenvironment of T-lymphoid tissues which is necessary for the differentiation and maturation of IDC.
Virchows Arch B Cell Pathol Incl Mol Pathol 1992
PMID:Induction of interdigitating reticulum cell-like differentiation in human monocytic leukemia cells by conditioned medium from IL-2-stimulated helper T-cells. 135 19

The crystal structure of the complex between neuraminidase from influenza virus (subtype N9 and isolated from an avian source) and the antigen-binding fragment (Fab) of monoclonal antibody NC41 has been refined by both least-squares and simulated annealing methods to an R-factor of 0.191 using 31,846 diffraction data in the resolution range 8.0 to 2.5 A. The resulting model has a root-mean-square deviation from ideal bond-length of 0.016 A. One fourth of the tetrameric complex comprises the crystallographic model, which has 6577 non-hydrogen atoms and consists of 389 protein residues and eight carbohydrate residues in the neuraminidase, 214 residues in the Fab light chain, and 221 residues in the heavy chain. One putative Ca ion buried in the neuraminidase, and 73 water molecules, are also included. A remarkable shape complementarity exists between the interacting surfaces of the antigen and the antibody, although the packing density of atoms at the interface is somewhat looser than in the interior of a protein. Similarly, there is a high degree of chemical complementarity between the antigen and antibody, mediated by one buried salt-link, two solvated salt-links and 12 hydrogen bonds. The antibody-binding site on neuraminidase is discontinuous and comprises five chain segments and 19 residues in contact, whilst 33 neuraminidase residues in eight segments have 899 A2 of surface area buried by the interaction (to a 1.7 A probe), including two hexose units. Seventeen residues in NC41 Fab lying in five of the six complementarity determining regions (CDRs) make contact with the neuraminidase and 36 antibody residues in seven segments have 916 A2 of buried surface area. The interface is more extensive than those of the three lysozyme-Fab complexes whose crystal structures have been determined, as judged by buried surface area and numbers of contact residues. There are only small differences (less than 1.5 A) between the complexed and uncomplexed neuraminidase structures and, at this resolution and accuracy, those differences are not unequivocal. The main-chain conformations of five of the CDRs follow the predicted canonical structures. The interface between the variable domains of the light and heavy chains is not as extensive as in other Fabs, due to less CDR-CDR interaction in NC41. The first CDR on the NC41 Fab light chain is positioned so that it could sterically hinder the approach of small as well as large substrates to the neuraminidase active-site pocket, suggesting a possible mechanism for the observed inhibition of enzyme activity by the antibody.(ABSTRACT TRUNCATED AT 400 WORDS)
J Mol Biol 1992 Sep 05
PMID:Refined crystal structure of the influenza virus N9 neuraminidase-NC41 Fab complex. 138 57

Non-glycine residues with positive theta-angles have been identified in four proteins, barley serine proteinase inhibitor CI-2, bacterial ribonuclease (barnase) of Bacillus amyloliquefaciens, hen egg white lysozyme and a basic protein from barley seed (barwin) by use of nuclear magnetic resonance spectroscopy. By accurate measurements of the coupling constant (3)JHNHalpha and integration of the nuclear Overhauser HN-Halpha cross peak, positive theta-angles could be determined reliably to 60 degrees +/- 30 degrees, in full agreement with the crystal structures for lysozyme, barnase and serine proteinase inhibitor CI-2. The work emphasizes that positive theta-angles can also occur in non-glycine residues and in the four proteins, positive theta-angles have been observed for the residue types aspartic acid, asparagine, arginine, serine, glutamine, histidine, tyrosine, tryptophan and phenylalanine. The measured (3)JHNHalpha coupling constants and the intensity of the intraresidue HN-Halpha NOEs agree well with the solution structures of three of the proteins, using the existing parametrization of the Karplus curve (Pardi, A., Billeter, M. and Wuthrich, K. (1984) J. Mol. Biol., 180, 741-751; Ludvigsen, S. Andersen, K.V. and Poulsen, F.M. (1991) J Mol. Biol., 217, 731-736).
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PMID:Positive theta-angles in proteins by nuclear magnetic resonance spectroscopy. 139 67

By display of antibody repertoires on the surface of a filamentous bacteriophage and selection of the phage by binding to antigen, we can mimic immune selection. Recently, by tapping the repertoire of rearranged V-genes from the peripheral blood lymphocytes of unimmunised donors, we succeeded in making human antibody fragments with different specificities, including both haptens and proteins, from the same library of phage. Now we have built a repertoire of human VH genes from 49 human germline VH gene segments rearranged in vitro to create a synthetic third complementarity determining region (CDR) of five or eight residues. The rearranged VH genes were cloned with a human V lambda 3 light chain as single chain Fv fragments for phage display, and the library of phage panned by binding to each of two haptens, 2-phenyl-5-oxazolone (phOx) or 3-iodo-4-hydroxy-5-nitrophenyl-acetate (NIP) coupled to bovine serum albumin (BSA). Many different antibody fragments were isolated which bound specifically to hapten, some with affinities in the micromolar range. The in vitro "immune response" to the hapten NIP was dominated by the 9-1 segment (VH3 family), and that to phOx by the VH26 segment (VH3 family) with an invariant aromatic residue (Tyr, Phe, Trp) at residue 97 of CDR3. However, the isolation of phage against protein antigens proved more elusive, with a single phage binding to human tumour necrosis factor, and none to bovine serum albumin, turkey egg-white lysozyme or human thyroglobulin. Nevertheless, the work shows that human antibody fragments with specific binding activities can be made entirely in vitro.
J Mol Biol 1992 Sep 20
PMID:By-passing immunisation. Human antibodies from synthetic repertoires of germline VH gene segments rearranged in vitro. 140 59

The mutant T4 phage lysozyme in which isoleucine 3 is replaced by proline (I3P) crystallizes in an orthorhombic form with two independent molecules in the asymmetric unit. Relative to wild-type lysozyme, which crystallizes in a trigonal form, the two I3P molecules undergo large hinge-bending displacements with the alignments of the amino-terminal and carboxy-terminal domains changed by 28.9 degrees and 32.9 degrees, respectively. The introduction of the mutation, together with the hinge-bending displacement, is associated with repacking of the side-chains of Phe4, Phe67 and Phe104. These aromatic residues are clustered close to the site of the mutation and are at the junction between the amino and carboxyl-terminal domains. As a result of this structural rearrangement the side-chain of Phe4 moves from a relatively solvent-exposed conformation to one that is largely buried. Mutant I3P also crystallizes in the same trigonal form as wild-type and, in this case, the observed structural changes are restricted to the immediate vicinity of the replacement. The main change is a shift of 0.3 to 0.5 A in the backbone of residues 1 to 5. The ability to crystallize I3P under similar conditions but in substantially different conformations suggests that the molecule undergoes large-scale hinge-bending displacements in solution. It is also likely that these conformational excursions are associated with repacking at the junction of the N-terminal and C-terminal domains. On the other hand, the analysis is complicated by possible effects of crystal packing. The different I3P crystal structures show substantial differences in the binding of solvent, both at the site of the Ile3-->Pro replacement and at other internal sites.
J Mol Biol 1992 Oct 05
PMID:Structure of a hinge-bending bacteriophage T4 lysozyme mutant, Ile3-->Pro. 140 94

The relationship between the bacteriophage lambda lysozyme (lambda L) and the C and V-type lysozymes has been investigated by sequence alignment, secondary structure prediction and pattern recognition methods. The alignment of the amino terminal part of lambda L with that of V-type lysozymes suggests that Glu19 is a residue essential for catalysis. Its mutation to Gln leads to a completely inactive enzyme. In the alignment of the sequence of lambda L with those of the C-type lysozymes a strongly homologous fragment of about 30 amino acid residues is detected. Taking into consideration this observation and the published structural alignments between C and V-type lysozymes, a repetition of the beta-sheet motif in lambda L is proposed. The multiple alignment draws the attention to a possible catalytic role for Asp34 that would be positioned in the middle of the second strand of the beta-sheet as in the C-type lysozymes. This role is confirmed by mutagenesis. The implications of these observations in terms of the evolutionary relationship between lambda L and the other lysozymes is discussed.
J Mol Biol 1992 Nov 20
PMID:Is the bacteriophage lambda lysozyme an evolutionary link or a hybrid between the C and V-type lysozymes? Homology analysis and detection of the catalytic amino acid residues. 145 62

Lysis protein T of phage T4 is required to allow the phage's lysozyme to reach the murein layer of the cell envelope and cause lysis. Using fusions of the cloned gene t with that of the Escherichia coli alkaline phosphatase or a fragment of the gene for the outer membrane protein OmpA, it was possible to identify T as an integral protein of the plasma membrane. The protein was present in the membrane as a homooligomer and was active at very low cellular concentrations. Expression of the cloned gene t was lethal without causing gross leakiness of the membrane. The functional equivalent of T in phage lambda is protein S. An amber mutant of gene S can be complemented by gene t, although neither protein R of lambda (the functional equivalent of T4 lysozyme) nor S possess any sequence similarity with their T4 counterparts. The murein-degrading enzymes (including that of phage P22) have in common a relatively small size (molecular masses of ca. 18,000) and a rather basic nature not exhibited by other E. coli cystosolic proteins. The results suggest that T acts as a pore that is specific for this type of enzyme.
Mol Gen Genet 1992 Nov
PMID:Lysis protein T of bacteriophage T4. 146

Genes encoding pre-protein and prepro-protein of wheat germ agglutinin isolectin 2 (WGA2) were chemically synthesized and expressed in the yeast Saccharomyces cerevisiae under the control of the ENO1 promoter. Yeast harboring either a pre-WGA2 or a prepro-WGA2 gene expression plasmid secreted a mature form of WGA2 into the culture medium. The amount of WGA2 secreted by the strain KS58-2Ddel, which has a ssl1 mutation causing a supersecretion of human lysozyme [Suzuki, K., Ichikawa, K. & Jigami, Y. (1989) Mol. Gen. Genet. 219, 58-64], was 20-fold greater than that secreted by the wild-type strain KK4. The recombinant WGA2 from the cells containing the prepro-WGA2 gene expression plasmid was purified to homogeneity by a three-step ion-exchange chromatography scheme. As in wheat, the N-terminal signal peptide of recombinant WGA2 purified from yeast culture was processed to form an N-terminal 5-oxoprolyl (pyroglutamyl) residue. Likewise, we found that the C-terminal pro-region of recombinant WGA2 had also been processed in yeast. Using electrospray ionization mass spectrometry, we found the processed C-terminus to be heterogeneous in both recombinant WGA2 purified from yeast and in authentic WGA2. The major component of the recombinant WGA2 contained two additional amino acids at its C-terminus compared to that of authentic WGA2. In spite of this difference in the C-terminus, the recombinant WGA2 exhibited a sugar binding activity that was indistinguishable from that of authentic WGA2.
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PMID:Expression and secretion of wheat germ agglutinin by Saccharomyces cerevisiae. 148 81

The interaction between hen lysozyme and urea has been investigated using 1H nuclear magnetic resonance spectroscopy. Chemical shift changes for resonances of a number of residues in the vicinity of the active site of the protein have been observed in the presence of urea prior to denaturation. These shifts are similar to those induced in the hen lysozyme spectrum by the specific binding of N-acetylglucosamine (GlcNAc) in site C of the active site cleft, indicating that urea and GlcNAc induce a similar conformational change in the enzyme. This implies that the conformational changes experienced by the enzyme on the binding of GlcNAc oligosaccharides are the consequence of interactions, possibly hydrogen bonding, involving the N-acetyl group of the sugar residue bound in site C, rather than the result of contacts between the protein and the pyranose rings of the oligosaccharides. This suggests that hen lysozyme employs an induced fit type mechanism to discriminate for N-acetylated saccharides as substrates.
J Mol Biol 1992 Sep 05
PMID:1H nuclear magnetic resonance studies of the interaction of urea with hen lysozyme. Origins of the conformational change induced in hen lysozyme by N-acetylglucosamine oligosaccharides. 152 4


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