In vivo glycosylation suppresses the aggregation of amyloidogenic hen egg white lysozymes expressed in yeast

The mutant hen egg white lysozymes Ile55Thr and Asp6bHis, corresponding to human amyloidogenic mutant lysozymes Ile56Thr and Asp67His, respectively, w ere secreted in Saccharomyces cerevisiae. The amyloidogenic mutants (155T a nd D66H) of hen egg white lysozymes were remarkably less soluble than that of the wild-type protein. To enhance the secretion of these mutants, we con structed the glycosylated amyloidogenic lysozymes (I55T/G49N and D66H/G49N) having the N-glycosylation signal sequence (Asn-X-Ser) by the substitution of glycine with asparagine at position 49, The secretion of these glycosyl ated mutant proteins is greatly increased in S. cerevisiae, compared with t hat of non-glycosylated type. Both the glycosylated mutants retained about 40% enzymatic activity when incubated at pH 7.4 for 1 that the physiologica l temperature of 37 degreesC whereas the non-glycosylated proteins eventual ly lost all activity under these conditions. These results suggest that the glycosylated chains could mask the beta -strand of amyloidogenic lysozymes from the intermolecular cross-beta -sheet association, thus improving the solubility of amyloidogenic lysozymes, (C) 2001 Federation of European Bioc hchemical Societies. Published by Elsevier Science B,V, All rights reserved .