Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.2.1.17 (lysozyme)
21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The locations of the periplasmic proteins of Escherichia coli on standard two-dimensional gel patterns are described. The periplasmic fractions were prepared by osmotic shock of plasmolyzed whole cells and by release during EDTA-lysozyme treatment of whole cells. Within this fraction of proteins, we identify nine binding proteins (leucine-specific, glutamate-aspartate, glutamine, cystine, galactose, maltose, xylose, ribose, and arabinose) in addition to leucine-isoleucine-valine binding protein, which has been previously identified (Bloch, P. L., Phillips, T. A., and Neidhardt, F. C. (1980) J. Bacteriol. 141, 1409-1420). The identifications are based upon genetic criteria, protein induction, and comigration with purified protein. The levels of these proteins are compared in strains K12, B, and HA12 (a derivative of W). A technique was developed for renaturation of the ligand binding sites of periplasmic binding proteins in denaturing two-dimensional gels. This technique was used to demonstrate that leucine-specific and cystine binding proteins both have different isoelectric points in different strains. Renaturation was also used to demonstrate that there are two different charged forms for glutamine binding protein.
...
PMID:Renaturation and identification of periplasmic proteins in two-dimensional gels of Escherichia coli. 675 51

Outer membrane proteins were derived from one rough and four smooth strains of Brucella abortus by sequential extraction of physically disrupted cells with N-lauroylsarcosinate and dipolar ionic detergent. Extraction of outer membrane proteins was ineffective, however, without predigestion with lysozyme. Three groups of proteins were present and could be separated in their native state by sequential anion-exchange chromatography and gel filtration. Membrane proteins contained substantial quantities of tightly adherent lipopolysaccharide which could be reduced but not eliminated by extraction of cells with trichloroacetic acid before disruption. Group 2 proteins, apparently trimers in their native state, gave rise to 43,000- and 41,000-molecular-weight bands after complete denaturation in sodium dodecyl sulfate. They were antigenically identical among all the strains, showed close resemblance in amino acid composition to each other and a general similarity to OmpF of Escherichia coli, and are proposed to be the porins of B. abortus. Group 3 proteins occurred as 30,000-molecular-weight bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, although additional bands were frequently observed in this region. In none of the strains did group 3 proteins manifest heat-modifiable characteristics. Proteins of different strains bore a high degree of similarity to each other in amino acid composition, except in methionine, isoleucine, tyrosine, and histidine. Differences occurred consistently in amino acid composition between group 2 and 3 proteins, and some of these correspond to differences between OmpF and OmpA. Group 2 and 3 proteins were antigenically distinct from each other, but the principal group 3 antigens were shared among all the strains. Despite the lack of heat modifiability, perhaps influenced by adherent lipopolysaccharide, group 3 proteins are proposed as counterparts to OmpA. Most of the group 1 proteins, minor components, were physically associated with those of group 3 unless in sodium dodecyl sulfate. Group 1 proteins produced a major band at 94,000 and exhibited heat modifiability. No evidence was found of a low-molecular-weight lipoprotein in the outer membrane of B. abortus, but this is not taken to exclude its occurrence.
...
PMID:Outer membrane proteins of Brucella abortus: isolation and characterization. 680 64

Since it has been uncertain whether residue 103 in hen egg-white lysozyme is aspartic acid or asparagine, we reexamined the identity of this residue. To avoid complication, the tryptic peptide T-13 (Ile 98-Arg 112) was further cleaved. The peptide containing residues Gly 102-Arg 112 was obtained by tryptic digestion of lysozyme modified at Asp 101 with diethylenetriamine. The peptide containing residues Ile 98-homoserine 105 was obtained by BrCN treatment of peptide T-13. Both Edman degradation of the former peptide and carboxypeptidase X digestion of the latter peptide identified residue 103 in hen egg-white lysozyme as asparagine.
...
PMID:Identification of residue 103 in hen egg-white lysozyme. 730 22

L-[4,5-3H]- or L-[U-14C]leucine was incorporated by Bacteroides thetaiotaomicron into acid-precipitable material even when the bacteria were treated with concentrations of tetracycline high enough to prevent growth. Similar results were obtained when L-[2,3,4-3H]valine or L-[4,5-3H]isoleucine was used instead of leucine. In bacteria which had been treated with tetracycline, the acid-precipitable label was not solubilized by treatment with protease, lysozyme, or deoxyribonuclease. However, virtually all of the label was extractable with chloroform-methanol, indicating that the label had been incorporated into membrane lipids. Since L-[1-14C]leucine was not incorporated into lipids, leucine was probably decarboxylated before incorporation. When a chloroform extract from bacteria which had been labeled with both [32P]phosphate and [3H]leucine was resolved into component phospholipids by two-dimensional thin-layer chromatography, 3H was incorporated into all of the phospholipids. When these phospholipids were deacylated, the 3H from leucine was associated with released fatty acids rather than with the head groups. Thus, it appears that B. thetaiotaomicron can utilize leucine and similar amino acids not only by incorporating them into protein but also by incorporating portions of these amino acids into membrane phospholipids.
...
PMID:Incorporation of leucine into phospholipids of Bacteroides thetaiotaomicron. 746 55

In order to understand the contribution of hydrophobic residues to the conformational stability of human lysozyme, five Ile mutants (Ile --> Val) in the interior of the protein were constructed. The thermodynamic parameters characterizing the denaturation of these mutant proteins were determined by scanning calorimetry, and the three-dimensional structure of each mutant protein was solved at high resolution by X-ray crystallography. The thermodynamic analyses at 64.9 degrees C and at pH 2.7 revealed the following. (1) The stabilities of all the mutant proteins were decreased as compared with that of the wild-type protein. (2) The changes in the calorimetric enthalpies were larger than those in the Gibbs energies, and were compensated by entropy changes. (3) The destabilization mechanism of the mutant proteins differs, depending on the location of the mutation sites. X-ray analyses showed that the overall structures of all the mutant human lysozymes examined were identical to that of the wild-type protein, and only small structural rearrangements were observed locally around some of the mutation sites. The most striking change among the mutant proteins was found in the mutant protein, 159V, which contains a new water molecule in the cavity created by the mutation. The thermodynamic stabilities of the mutant proteins are discussed in light of the high-resolution X-ray structures of the wild-type and five mutant human lysozymes examined.
...
PMID:Contribution of hydrophobic residues to the stability of human lysozyme: calorimetric studies and X-ray structural analysis of the five isoleucine to valine mutants. 747 60

The predominant T cell epitope of hen egg lysozyme (HEL) in high-responder C3H mice has been previously identified as the HEL 46-61 region. In contrast, this region is poorly recognized by T cells from low-responder C57BL/6 mice upon immunization with HEL. In previous studies, we have demonstrated that several C57BL/6 derived T cell hybridomas reactive to this epitope and other HEL epitopes preferentially recognize phosphorylcholine (PC)-conjugated HEL over unconjugated HEL. To understand the mechanisms involved in this difference of T cell recognition, we have further analysed the reactivity of T cells and T cell hybridomas from low-responder C57BL/6 mice. T cells from HEL-immunized mice were preferentially reactive to HEL 47-60. These results suggest a potential deficiency in generating an appropriate T cell epitope from the 46-61 region of native HEL in low-responder C57BL/6 mice. The minimal T cell epitope of this region was defined as HEL 51-60 using the PCH4.1 T hybridoma clone. This minimal epitope represents a single amino acid shift from the minimal epitope of HEL high-responder C3H mice (HEL 52-61). Various peptides representing this region were synthesized with single alanine substitutions at each position. The residues at positions 51, 52, 53 and 57 of HEL appear to be involved in Ia binding and the residues at 55 and 56 in contracting the TCR. T cell reactivity to HEL 51-61 peptides with various substitutions at position 61 strongly suggest that primarily the size of the C-terminal residue interferes with binding to the Ia molecules of low-responder mice. In addition, substitutions of the TCR contacting residues at positions 55 and 56 with similar residues (isoleucine-->leucine or leucine-->isoleucine) significantly increased the T cell reactivity, suggesting a low reactivity with the native residues. Therefore, the requirement of many residues in the T cell epitope for interaction with Ia, the necessity for additional Ag processing to facilitate Ia binding, and the low affinity of the TCR contacting residues may together render C57BL/6 mice unresponsive to the HE 46-61 region.
...
PMID:T cell epitope recognition involved in the low-responsiveness to a region of hen egg lysozyme (46-61) in C57BL/6 mice. 751 4

The specificity of hen egg-white lysozyme (HEL)-reactive rabbit antibodies induced by the peptide loop I.II (sequences 57-107 containing Cys64-Cys80 and Cys76-Cys94) of HEL was clarified by analyzing their cross-reactions with various avian lysozymes and their reaction with synthetic peptides (sequences 59-82) in which alanine was substituted for the amino acid at certain positions. The Arg-68 residue of HEL plays a dominant role in the binding, while Gly-71, Ser-72, Arg-73, and Pro-79 also contribute to the binding of two anti-Ploop I.II antibodies (rabbit number 125 and 126). These residues, although remote in sequence, are grouped together in the crystal structure of HEL and may form an area of contact with the antibody. Contributions by Trp-63, Ile-78, and Asn-77 to the binding of the two antibodies to HEL were excluded. These results support the idea that the anti-Ploop I.II antibodies recognize a conformational type of epitope which is similar to that of native HEL. The immunogenicity of the reduced and alkylated form of Ploop I.II was also tested, but it failed to induce an HEL-reactive antibody.
...
PMID:Characteristics of the epitope of protein-reactive anti-peptide antibodies. 768 42

The binding of N,N',N",N"'-tetraacetylchitotetraitol [(GlcNAc)4-ol] to hen egg white lysozyme was investigated by fluorescence and 1H NMR spectroscopy. From observation of changes in the fluorescence intensity, the association constants of (GlcNAc)4-ol and (GlcNAc)3 were found to be 0.70 x 10(5) and 1.07 x 10(5) M-1, respectively, at pH 5.0 and 30 degrees C. The lack of a substantial difference between the association constants suggests that the binding mode of the (GlcNAc)3 moiety of (GlcNAc)4-ol is basically similar to that of (GlcNAc)3, but that the N-acetylglucosaminitol residue of (GlcNAC)4-ol does not interact significantly with lysozyme. On the other hand, 1H NMR spectroscopy revealed a minor difference in the binding modes of the two saccharides. For most of the 1H signals responding to saccharide binding, such as those of Trp 63 H2, Trp 28 H5, and Ile 98 H gamma 1, the chemical shift changes induced by (GlcNAc)4-ol were almost identical to those induced by (GlcNAc)3. However, the effect of binding on the signals of Asn 59 H alpha and Trp 108 indole N1H, which are located near subsite C, was different for (GlcNAc)4-ol and (GlcNAc)3. Thus it is inferred that the binding mode of the first sugar residue of (GlcNAc)4-ol to subsite C is somewhat different from that of (GlcNAc)3.
...
PMID:Binding mode of N,N',N",N"'-tetraacetylchitotetraitol to hen egg white lysozyme. 769 63

We report here a comprehensive infrared spectroscopic study of the interactions between the anesthetic nitrous oxide (N2O) and six proteins: lysozyme, cytochrome c, myoglobin, hemoglobin, serum albumin, and cytochrome c oxidase. Sites occupied by N2O molecules within these proteins were characterized. Three types of hydrophobic sites were found within the proteins. One with nu 3 near 2225 cm-1 is likely to be near peptide bond carbonyls; one with nu 3 near 2219 cm-1 may be near a benzene-like structure such as the side chains of phenylalanine and tyrosine; and the other with nu 3 near 2215 cm-1 is likely to be in a nonpolar alkane-like environment provided by the side chains of Leu, Ile, and Val residues. The amount of N2O molecules bound to myoglobin increases as the pH decreases from 9.2 to 5.2. N2O-protein interactions produced no detectable changes in the ligand-binding pockets of myoglobin, hemoglobin, and cytochrome c oxidase. N2O-induced secondary structure changes were detected only in the fully reduced cytochrome c oxidase, not in the fully oxidized oxidase and the other five proteins. N2O-induced conformational changes in the alpha beta-interface of hemoglobin and the h2 and h3 alpha-helices of human serum albumin were detected by monitoring the S-H stretch vibrations of cysteine residues. These findings provide direct evidence that anesthetic N2O interacts with proteins and occupies sites in the interior of the proteins.
...
PMID:Characterization of sites occupied by the anesthetic nitrous oxide within proteins by infrared spectroscopy. 792 38

Significant advances were made this year in the understanding of serum amyloid A isotypes and in the definition of different amyloid light-chain proteins. Increasing numbers of hereditary amyloid-related transthyretin mutations have been reported (more than 30 to date). Two new hereditary amyloid proteins in several different kinships have appeared, ie, fibrinogen A alpha and lysozyme, each with a single point mutation. Both were found in patients with non-neurogenic hereditary amyloidosis with severe nephropathy. In islet amyloid polypeptide, the amyloid of adult-onset diabetes, the amino-acid sequence Ala-Ile-Leu-Ser at positions 25 to 28 appears to be critical for fibrillogenesis.
...
PMID:Proteins of the systemic amyloidoses. 803 80


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---