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 antigenic structural features of alpha-lactalbumin have been investigated using a radioimmunoassay, peptide inhibition of the quantitative precipitin reaction, and by immunodiffusion analysis after chemical modification of the molecule. Antigenic activity (in rabbits) was localized to several peptic fragments and the single arginine residue of bovine alpha-lactalbumin. Antigenic activity was also found to be associated with the single methionine residue. A peptic fragment containing a disulfide loop was found to possess antigenic activity in both bovine and goat alpha-lactalbumin. Radioimmunoassay cross-reactivity between the alpha-lactalbumins is correlated with amino acid sequence similarities; bovine alpha-lactalbumin antiserum cross-reacts with goat alpha-lactalbumin more extensively than with human alpha-lactalbumin, while the more distantly homologous protein, chicken lysozyme, does not cross-react at all. Nevertheless our data indicate that the alpha-lactalbumins and lysozyme share a similar distribution of antigenic determinants on their surfaces.
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PMID:Immunochemical studies on alpha-lactalbumin. 619 Dec

Earlier studies have indicated the marked resistance of two pronase endopeptidases to denaturation in high concentrations of urea or guanidine hydrochloride (Siegel, S., and Awad, W. M., Jr. (1973) J. Biol. Chem. 248, 3233--3240). One component has only a single residue of lysine and the other has none. The consideration arose that lysine-containing peptide segments may be less stable than those containing arginine because of the fluctuations of the side groups of the former residue. The small epsilon amino groups may not be able to sustain solvation of the hydrophobic arm in an aqueous medium. Arginine residues have shorter hydrophobic arms, larger hydrophilic groups, and higher pKa values and, thus may be less motile than lysine. The hypothesis was tested by guanidination of seven globular proteins (bovine carbonic anhydrase, chymotrypsinogen, alpha-lactalbumin, serum albumin, ribonuclease, hen egg lysozyme, and horse heart cytochrome c). Conversion of lysine residues to homoarginine was between 90 and 99%. Tritium-hydrogen isotope exchange revealed that all proteins except lysozyme demonstrated reduced out-exchange after guanidination. The results with lysozyme were not unexpected since only this protein has a high arginine to lysine ratio. These findings suggest that high arginine to lysine ratios contribute to protein stability.
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PMID:Stabilization of proteins by guanidination. 625 87

Nucleotide sequence analyses of essentially full-length copies of human and guinea-pig pre-alpha-lactalbumin cDNAs contained within recombinant plasmids, (i) confirm the presence of 19 amino acid hydrophobic amino terminal peptide extensions encoded within each mRNA; and (ii) provides evidence for the existence of a minor variant of guinea-pig alpha-lactalbumin mRNA encoding a protein with a 36 residue carboxyl-terminal extension. Comparison of the nucleotide sequence within the coding region of the human, and the predominant guinea-pig pre-alpha-lactalbumin mRNAs, with the analogous region of hen pre-lysozyme mRNA provides compelling evidence that all have evolved from a common ancestral gene.
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PMID:Comparison of the nucleotide sequence of cloned human and guinea-pig pre-alpha-lactalbumin cDNA with that of chick pre-lysozyme cDNA suggests evolution from a common ancestral gene. 628 5

Main points given in the above reports can be summarized as follows. Multiple unfolded forms exist for lysozyme as well as for RNase. The existence of fast- and slow-folding forms appears to be a general phenomenon; it has been confirmed for a number of globular proteins, which contain proline residues. The major slow refolding reaction of RNase A is a sequential process via structural intermediates. A rapidly formed intermediate has also been detected on the direct UF----N refolding pathway of lysozyme. The activated state for folding of lysozyme shows a conformation similar to the native protein in terms of packing of hydrophobic groups. This suggests that, in terms of compactness, the rate-limiting step occurs at a late stage of the refolding process. A protein homologous to lysozyme, alpha-lactalbumin, shows similar kinetics although alpha-lactalbumin shows an apparent equilibrium unfolding intermediate. The location of the rate-limiting step close to the native state has also been suggested for other proteins. It still remains open whether this is a general property of protein folding reactions. As shown for the unfolding of Mb, the multi-probe kinetic measurements will be a powerful tool for investigating the mechanism of folding, in particular for characterizing structural kinetic intermediates. The dynamics of local fluctuations of a well-defined part of RNase S can be monitored by NMR measurements of NH proton exchange. An increasing number of experimental and theoretical studies are focussing on the problem of protein dynamics. Application of NMR methods to protein folding should give extensive information about the structure of intermediates, which cannot be given by other techniques.
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PMID:Experimental studies of folding kinetics and structural dynamics of small proteins. 639 21

In a study of factors that influence the remaining secondary structure of reduced chicken eggwhite lysozyme, N-acetyl-D-glucosamine (NAG) and N,N'-diacetylchitobiose (di-NAG) were found to alter the circular dichroic (CD) spectrum of the reduced protein and its carboxymethyl derivative (Cml). Thus, negative ellipticities in the far u.v. were greater in the presence of the analogs, with NAG being the more effective. For Cml, curve fitting analysis of the CD data indicated an increased helical content in the presence of NAG by an average of 3% of the chain length, while beta-structure decreased by an equivalent amount. Other compounds structurally related to NAG produced no similar effects on the CD spectrum of Cml, nor were comparable effects of NAG in evidence on the Cm reduced derivatives of ribonuclease, chymotrypsin, wheat germ agglutinin, or alpha-lactalbumin. The effect therefore appears specific between NAG and Cml. Conversion of the tryptophan residue at Position 62 of Cml to the oxindolealanyl derivative prevented these effects of NAG, and this residue may therefore participate in the interaction. During a 4-day incubation at room temperature, the analog preserved the CD spectrum of Cml as well as its concentration. This effect was nearly specific when compared with other Cm reduced proteins and with other carbohydrates. Only one, N-acetyl mannosamine, was effective in preserving the concentration of Cml, but not the CD spectrum. Since D-glucosamine was entirely without effect on either the CD spectrum of Cml or on its change during incubation, the acetyl group appears essential for the NAG-Cml interaction. The specificity between NAG and Cml is tentatively accounted for in terms of interactions with the primary structure, rather than with the remaining secondary structure.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Evidence for interaction of substrate analogs with chicken eggwhite lysozyme after exhaustive reduction of disulfide bonds. 651 17

The interaction of bovine pancreatic alpha-chymotrypsin with dimyristoyl phosphatidylcholine (PC) vesicles was measured turbimetrically. The protein interacted with the vesicles at NaCl concentrations of above 0.8 M. The turbidity reached a plateau on increase in the amount of either the protein or the vesicles in the presence of a fixed amount of the other component. The precipitates formed contained both PC and protein in ratios varying with the initial amount of each component. On mixing chymotrypsin and PC vesicles, time-dependent turbidity increase was high at below pH 2.5, but relatively small at neutral and alkaline pH values. Apolar interaction between the two components was confirmed by demonstrating an increase in fluorescence intensity of chymotrypsin in the presence of the PC in 1 M NaCl. The turbidity of a mixture of PC vesicles and bovine serum albumin (BSA) increased even in the absence of 1 M NaCl, whereas the turbidities of mixtures of the vesicles and lysozyme or alpha-lactalbumin did not change with time in the presence of 1 M NaCl at pH 8.0.
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PMID:Apolar interaction of alpha-chymotrypsin with dimyristoyl phosphatidylcholine vesicles. 654 42

1. A comparison is made of gel electrophoretic patterns of the "whey" proteins of the milk of red (Macropus rufus) and eastern grey (Macropus giganteus) kangaroos at various stages of lactation. Qualitative and quantitative changes occur with time during the mature phase of lactation of both types. Their onset is related solely to the stage of lactation. "Whey" proteins are isolated and characterised and the nature of protein changes determined for the first time. 2. The anodic electrophoretic pattern is divided into 6 main zones (designated A F in order of decreasing mobility) and 2 cathodic zones (G and H) that are only detected in the milk of M. giganteus. 3. Zones A, B and C are milk specific. Zone B is present throughout lactation in both species and is an alpha-lactalbumin. Zones A and C are present only in late lactation, zone C, usually, but not always, appearing first. Zone A is an alpha-lactalbumin in M. giganteus, but is not an alpha-lactalbumin in M. rufus. Zone C appears to be the same protein in both species and is possibly a beta-lactoglobulin. 4. Zone D is kangaroo serum albumin and zone E is possibly a beta 2-microglobulin. Zone F contains three main iron (III) binding bands whose relative intensity varies with stage of lactation. Their intensity differs from the corresponding blood serum transferrin bands. 5. Zone H of Macropus giganteus is a lysozyme. 6. Lactose is present in the milk, but is not the principal sugar. 7. The significance of the results is discussed.
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PMID:"Whey" proteins of milk of the red (Macropus rufus) and eastern grey (Macropus giganteus) kangaroo. 660 Sep 92

The secondary structure of 16 type c lysozymes, 2 type g lysozymes, phage T4 lysozyme and bovine alpha-lactalbumin have been estimated according to the method of Chou and Fasman (1978). The prediction has been done on the partial sequence of lysozymes from three insects and tortoise egg-white lysozyme. From these studies, patterns of common secondary structure domains on lysozymes have been developed. These patterns have been compared attending to the active site and the antigenic loop of the hen enzyme of which three-dimensional structure is known. The three-dimensional structures of phage T4 and hen egg-white lysozymes have common alpha-carbon backbone domains being that also observed by these predictions. Immunological results are also discussed in terms of secondary structure homologies.
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PMID:Comparative study on the secondary structure of lysozymes from different sources. 669 87

Attempts at isolating individual human milk proteins showed that cross interactions made it difficult to obtain of homogeneous components. A new method was devised, based on complete precipitation of milk proteins with saturated ammonium sulphate and progressive solubilization of the precipitate on a column of Sephadex G10 with a linear gradient of ammonium sulphate (from saturation to water). Three fractions were obtained. The first contained lactoferrin, serum albumin, lysozyme and traces of alpha-lactalbumin. Lysozyme could be obtained free from contaminants by chromatography on Ultrogel AcA 54. Lactoferrin and serum albumin coeluting as a single peak, were separated by a further chromatography on DEAE-cellulose. From the other two fractions recovered on Sephadex G10, it should be possible to prepare immunoglobulins, alpha-lactalbumin and the bulk of caseins. The homogeneity of the preparations of lysozyme, lactoferrin and serum albumin was assessed by SDS polyacrylamide gel electrophoresis, acrylamide agarose electrophoresis and immunoelectrophoresis.
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PMID:[A new method for human milk protein separation]. 682 Nov 60

The heat-stable polypeptide ATP-dependent proteolysis factor 1 (APF-1) of the reticulocyte proteolytic system forms covalent compounds with proteins in an ATP-requiring reaction. APF-1 and lysozyme, a good substrate for ATP-dependent proteolysis, form multiple conjugates, as was shown by comigration of label from each upon gel electrophoresis. Multiple bands were also seen with other substrates of the ATP-dependent proteolytic system, such as globin or alpha-lactalbumin. Analysis of the ratio of APF-1 to lysozyme radioactivities and of the molecular weights of the bands indicated that they consist of increasing numbers of the APF-1 polypeptide bound to one molecule of lysozyme. The covalent linkage is probably of an isopeptide nature, because it is stable to hydroxylamine and alkali, and polylysine is able to give conjugates of APF-1. Removal of ATP after formation of the 125I-labeled APF-1 conjugates with endogenous proteins caused the regeneration of APF-1, indicating presence of an amidase. This reaction is thought to compete with proteases that may act on APF-1-protein conjugates, especially those containing several APF-1 ligands. A sequence of reactions in which the linkage of APF-1 to the substrate is followed by the proteolytic breakdown of the substrate is proposed to explain the role of ATP.
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PMID:Proposed role of ATP in protein breakdown: conjugation of protein with multiple chains of the polypeptide of ATP-dependent proteolysis. 699 Apr 14


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