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)

A lysozyme isolated from the milk of a monotreme, the echidna, Tachyglossus aculeatus multiaculeatus, has been crystallized (space group P2(1), with unit-cell dimensions a = 37.1, b = 42.0, c = 38.1 A, beta = 91 degrees and Z = 2) and the structure refined to an R value of 0.167 for all measured data in the resolution range 7.0-1.9 A. It had previously been inferred from sequence homology with alpha-lactalbumins that echidna milk lysozyme (EML) would bind one calcium ion per molecule. This has been confirmed in the present study in which the largest peak in a difference Fourier synthesis is associated with a calcium ion. The calcium binding site of EML is very similar to that observed in baboon and human alpha-lactalbumins, and in a human lysozyme engineered to contain a calcium-binding site. The overall fold of the protein is similar to that of chick-type lysozymes. EML, like pigeon lysozyme, has only 125 residues terminating at a cysteine but in EML this forms a disulfide with a cysteine at residue 9 whereas the equivalent cysteine residue in all other lysozymes of known sequence occurs at position 6. These changes cause some minor structural rearrangements. The binding of calcium appears to have had little effect on the polypeptide backbone conformation and caused only small changes in the conformation of side chains coordinating the calcium ion. A homology modelling study [Acharya, Stuart, Phillips, McKenzie & Teahan (1994). J. Protein Chem. 13(6), 569-584] correctly predicted the overall structure of EML and the nature of its calcium binding site but generally failed to model some more subtle differences observed in the EML structure as evidenced by the fact that the homology model more closely resembles the starting structure from which the model was derived than it does the crystal structure.
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PMID:Structure of the calcium-binding echidna milk lysozyme at 1.9 A resolution. 1529

Shockman, Gerald D. (Temple University, Philadelphia, Pa.), J. Stuart Thompson, and Margaret J. Conover. Replacement of lysine by hydroxylysine and its effects on cell lysis in Streptococcus faecalis. J. Bacteriol. 90:575-588. 1965.-Hydroxylysine was not significantly incorporated by Streptococcus faecalis ATCC 9790 or 8043 until exponential growth ceased as a result of lysine exhaustion. Uptake was then rapid and virtually complete within 1 hr. Lysine absence, rather than physiological age, seemed to be the governing factor. Hydroxylysine uptake rapidly reached a peak in the acid-soluble fraction, suggesting a precursor role for substances in this fraction. Substitution of hydroxylysine for lysine was much more efficient in mucopeptide synthesis than in protein synthesis. In wall medium, less than 1% of the incorporated hydroxylysine was found in the protein fraction. Addition of lysine to both growth and wall media inhibited both further hydroxylysine uptake and transfer of hydroxylysine from acid-soluble to mucopeptide or protein fractions. Hydroxylysine resulted in decreased penicillin susceptibility only after it was postexponentially incorporated. This effect was physiologically similar to that seen after threonine deprivation or chloramphenicol treatment. Hydroxylysine incorporation increased resistance to autolysis, but failed to decrease lysozyme susceptibility when measured after heat inactivation of autolysis. Electron microscopy of negatively stained cells showed increased thickness of cell walls containing hydroxylysine. Thus, most of the effects of replacement of lysine by hydroxylysine resemble those seen after deprivation of a nonwall amino acid (e.g., threonine or valine) or after chloramphenicol treatment. Each of these conditions results in inhibition of protein synthesis while permitting cell-wall synthesis to continue, resulting in autolysis-resistant, thick-walled cells.
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PMID:Replacement of Lysine by Hydroxylysine and Its Effects on Cell Lysis in Streptococcus faecalis. 1656 51