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Title: Stability effects associated with the introduction of a partial and a complete Ca(2+)-binding site into human lysozyme
Authors: Haezebrouck, P ×
De Baetselier, A
Joniau, Marcel
Van Dael, Herman
Rosenberg, S
Hanssens, Ignace #
Issue Date: Jul-1993
Series Title: Protein engineering vol:6 issue:6 pages:643-9
Abstract: Two mutants of human lysozyme were synthesized. Mutant A92D, in which Ala92 was substituted by Asp, contains a partial Ca(2+)-binding site and mutant M4, in which Ala83, Gln86, Asn88 and Ala92 were replaced by Lys, Asp, Asp and Asp respectively, contains the complete Ca(2+)-binding site of bovine alpha-lactalbumin. The Ca(2+)-binding constants of wild type human lysozyme and of mutants A92D and M4, measured at 25 degrees C and pH 7.5, were 2(+/- 1) x 10(2) M-1, 8(+/- 2) x 10(3) M-1 and 9(+/- 0.5) x 10(6) M-1 respectively. Information gathered from microcalorimetric and CD spectroscopic measurements indicates that the conformational changes of the M4 mutant lysozyme, induced by Ca2+ binding, are smaller than those observed for bovine alpha-lactalbumin and for the Ca(2+)-binding equine lysozyme. At pH 4.5, the thermostability of both the apo and Ca2+ forms of the A92D human was decreased in comparison with that of native human lysozyme. In particular, within the apo form of this mutant an alpha-helix-containing sequence was destabilized. In contrast, at the same pH the thermostability of the apo and Ca2+ forms of the M4 mutant lysozyme was increased. The epsilon-ammonium group of the Lys83 side chain is assumed to be responsible for the stabilization of the apo form of this mutant.
URI: 
ISSN: 0269-2139
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Faculty of Science, Campus Kulak Kortrijk
Faculty of Medicine, Campus Kulak Kortrijk
× corresponding author
# (joint) last author

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