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

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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)

MHC proteins are polymorphic cell surface glycoproteins involved in the binding of peptide Ag and their presentation to T lymphocytes. The polymorphic amino acids of MHC proteins are primarily located in the N-terminal domains and are thought to influence T cell recognition both by influencing the binding of peptide Ag and by direct contact with the T cell receptor. In order to determine the relative importance of individual polymorphic amino acids in Ag presentation, a number of groups have taken the approach of interchanging polymorphic amino acids between different alleles of MHC protein in an attempt to define which of the polymorphisms influence peptide binding and which influence T cell recognition by direct contact with the TCR. The peptide OVA323-339 has been previously shown to bind to the MHC class II protein Ad and to have a much lower affinity for Ak, whereas the peptide hen egg lysozyme 46-61 binds well to Ak and poorly to Ad. In the present report, we have analyzed the ability of purified wild-type MHC class II proteins as well as the ability of three different hybrid molecules between Ad and Ak to bind and present these peptides. We find that the alpha-chain of the MHC class II protein plays a critical role in the binding of HEL46-61 and confers the specificity for binding OVA323-339, regardless of which beta-chain is present. We also find that the beta-chain region 65-67 does not control the specificity of peptide binding to the MHC protein, but is important in T cell responses to preformed MHC-peptide complexes, suggesting a role for this region in contacting the TCR.
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PMID:Functional mapping of MHC class II polymorphic residues. The alpha-chain controls the specificity for binding an Ad-versus an A k-restricted peptide and the beta-chain region 65-67 controls T cell recognition but not peptide binding. 184 39

Two different antigen-specific radiation leukemia virus (RadLV)-transformed suppressor T-cell clones, LH8.105 and LA41, exhibiting anti-lysozyme and anti-acetylcholine-receptor suppressor activity, respectively, have been examined for rearrangement and expression of genes encoding the alpha and beta chains of the T-cell receptor for antigen. LH8.105 cells express the T-cell-receptor polypeptides, as shown by specific immunoprecipitation. In both cell lines, potentially functional transcripts of alpha- and beta-chain genes are detected by RNA blot analysis. These suppressor T-cell clones exhibit alpha-chain gene rearrangements, deletion of both alleles of the constant-region (C) gene segment C beta 1, and rearrangement of the two alleles of C beta 2 when analyzed by Southern blot hybridization. Restriction analysis suggests that the DNA rearrangement is beyond the second joining-region (J) minigene of the J beta 2 cluster. These results establish that at least some mouse suppressor T-cell clones, like helper and cytotoxic T lymphocytes, rearrange and transcribe the genes coding for the alpha and beta chains of the antigen-specific T-cell receptor.
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PMID:Rearrangement and expression of the alpha- and beta-chain genes of the T-cell antigen receptor in functional murine suppressor T-cell clones. 293 34

Goblet-cell carcinoids are particular mucus-producing tumors combining features of typical carcinoids and adenocarcinomas. The immunoreactivity of five goblet-cell carcinoids of the appendix and one tumor of the ileum for 5-hydroxytryptamine (5-HT, serotonin), glucagon, somatostatin, substance P (SP), neuron-specific enolase (NSE), lysozyme, secretory component (SC) and carcino-embryonic antigen (CEA) was compared with that of the mucosa of the appendix (n = 24) and ileum (n = 12), and of typical carcinoids (appendix: n = 10; ileum: n = 3). The goblet-cell carcinoids were consistently lysozyme-, SC- and CEA-reactive and contained weakly NSE reactive endocrine cells, while typical carcinoids were lysozyme-, SC- and CEA-negative, but strongly NSE- reactive. Two goblet-cell carcinoids were glucagon-reactive, one displayed SP-reactivity, one malignant tumor was reactive to the alpha-chain of glycoprotein hormones; six of ten typical appendix carcinoids were SP reactive, as were the three typical ileum carcinoids. Using the immunogold technique combined with the alcian-blue reaction, the presence of 5-hydroxytryptamine (5-HT) and mucus was demonstrated within the same cell. These findings suggest histogenetic differences between goblet-cell carcinoids and typical carcinoids; the former are possibly derived from undifferentiated stem cells, whereas the latter probably arise from endocrine cells in the mucosal stroma.
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PMID:Combined production of mucus, amines and peptides by goblet-cell carcinoids of the appendix and ileum. 648 83

A method is described for the production of T-cell lines and clones specific for solubilized Trichinella spiralis antigens. These T cells are antigen-specific and do not respond to challenge with a third party antigen (lysozyme). The proliferation responses of the cloned T cells are specifically inhibited by anti-I-E but not by anti-I-A subregion monoclonal reagents. The inhibition patterns obtained are consistent with cis-gene complementation in B10.K cells involving the Ek beta-chain and the Ek alpha-chain of the I-E molecule. Inhibition is obtained with an Ek beta-specific monoclonal antibody (H9-14.8) but not with an Ak beta-specific monoclonal antibody (10-2.16). Inhibition was also observed with Ia.7-specific (H40-242) or Ia.22-specific (17-3-3) monoclonal antibodies. The inhibition patterns were confirmed by antigen presentation experiments using recombinant inbred mice. Only B10.K (Ek beta Ek alpha) spleen cells and not B10.A(5R) (Eb beta Ek alpha) or B10.S(9R) (Es beta Ek alpha) spleen cells could effectively present T. spiralis antigens. The role of "hybrid" Ia molecules in the immune response to T. spiralis is discussed.
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PMID:Cloned T cells recognize Trichinella spiralis antigen in association with an Ek beta Ek alpha restriction element. 660 15

The class II molecules of the MHC bind processed Ag fragments (peptides) for presentation to T cells, but the role of individual MHC residues in binding these peptides has not been entirely defined. A panel of 27 mutant I-Ak transfectants was analyzed for the capacity to bind 2 unrelated peptides. The main peptides examined were hen egg lysozyme residues 48-62 and heat shock protein (hsp70) to residues 28-41. Alanine substitutions of sites in the alpha-helical region of the I-Ak alpha-chain altered the ability of this class II protein to bind both peptides. Of the 27 substitutions tested, nine caused a decrease in peptide binding while only three caused an increase in peptide binding. The stabilities of these altered I-Ak-peptide complexes were also examined on SDS-Page. Complexes with lowered stabilities were observed after only four substitutions, and in all four cases this loss of stability was accompanied by a loss in hen egg lysozyme or hsp70 peptide-binding ability. Further, three of these residues lie in the short extended strand at the N terminus of the alpha-helix of the alpha 1 domain, suggesting that this region of I-Ak molecule may be critical for the formation of stable peptide-MHC complexes.
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PMID:Amino acid residues on the I-Ak alpha-chain required for the binding and stability of two antigenic peptides. 859 59

Hereditary systemic amyloidosis is caused by deposition of genetically variant proteins as amyloid fibrils. The types that present with renal disease are usually associated with mutations in the genes for either apolipoprotein AI, apolipoprotein AII, lysozyme or fibrinogen A alpha-chain. These diseases are inherited in an autosomal dominant manner with variable penetrance, and can present clinically at any time from the teen years to old age, though usually in mid-adult life. Hereditary amyloidosis is uncommon, but its precise characterization has major implications for patient management and genetic counseling, and it has been an extremely valuable model for elucidating the pathogenesis of amyloid deposition generally. The amyloidogenic variant proteins associated with hereditary amyloidosis are less stable than their normal wild type counterparts and even under physiological conditions can populate partly unfolded states, involving loss of tertiary or higher order structure, which readily aggregate with retention of beta-sheet secondary structure into protofilaments and fibrils. The clinical phenotype of hereditary renal amyloid is non-specific and is readily misdiagnosed as acquired AL amyloidosis. Indeed, we have lately demonstrated that five percent of patients with apparent sporadic amyloid have hereditary fibrinogen A alpha-chain amyloidosis associated with the valine 526 variant. Penetrance of this particular mutation is extremely low in most families obscuring the genetic etiology, but the renal histology is very characteristic showing substantial accumulation of amyloid within enlarged glomeruli, but none in blood vessels or the interstitium. DNA analysis is now performed routinely in UK National Amyloidosis Centre in patients with systemic amyloidosis in whom AA or AL fibril type cannot be definitively verified.
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PMID:Hereditary systemic amyloidosis with renal involvement. 1283 50

We aimed to reassess renal amyloidosis in kidney biopsies with a focus on possibly misclassified or unclassified cases and changes in the prevalence of different amyloid types. Two hundred thirty-three kidney biopsies obtained from 231 patients diagnosed with amyloid during the period from 1990 to 2007 years were included in this retrospective study. Amyloid was identified by Congo red staining and polarization microscopy. Immunohistochemical classification was made with antibodies directed against AA amyloid, apolipoprotein A1, fibrinogen, lysozyme, lambda-light chain, kappa-light chain, beta2-microglobulin, transthyretin, and amyloid P-component. Amyloid was present in each biopsy as vascular, tubulo-interstitial and/or glomerular deposits. Immunoglobulin light chain-derived (AL) amyloidosis was most prevalent and diagnosed in 123 (53.2%) patients. It was categorized into AL amyloid of lambda-light chain (ALlambda) [105 (85.4%) patients] and kappa-light chain origin (ALkappa) [10 (8.1%)]. The amyloid deposits of 8 (6.5%) patients were not clearly distinguishable into ALlambda amyloid or ALkappa amyloid and categorized as AL amyloid, not otherwise specified. Reactive systemic amyloid A (AA) amyloidosis was the second most common type and was found in 93 patients (40.3%). Overall 7 patients were found to suffer from fibrinogen A alpha-chain-[amyloid of fibrinogen (AFib); 4 (1.7%) patients], transthyretin-[amyloid of transthyretin (ATTR); 2 (0.9%)], or apolipoprotein A1-derived (AApoAI) amyloidosis [1 (0.4%)]. In 8 patients (3.4%) the amyloid deposits remained unclassifiable. After additional immunostaining and further clinical information the diagnoses of 12 patients (5.1%) were modified (2 ALlambda amyloid, 4 ALkappa amyloid, 1 amyloid unclassified, 3 mixed-type amyloidosis, AA+ATTR, ALlambda+ATTR, and ALkappa+ATTR, 1 AFib, and 1 AApoAI). Although the histologic and immunohistochemical reevaluation confirmed the classifications in 221 (95.7%) patients. Renal amyloidosis is most commonly of ALlambda-origin, followed by AA amyloidosis. AFib amyloidosis was found to be the most prevalent type of hereditary renal amyloidosis, illustrating the necessity of a thorough classification of the amyloid proteins.
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PMID:Prevalence and origin of amyloid in kidney biopsies. 1956 48

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