Hexokinase PII: Structural analysis and glucose signalling in the yeast Saccharomyces cerevisiae

Hexokinase PII (Wxk2) is a yeast glucose phosphorylating enzyme that, besid es its role in glycolysis, seems to have an additional role in glucose sign alling. To study the domains in Hxk2 that may participate in this latter pr ocess, we have constructed 11 mutant alleles using site-directed mutagenesi s. Six of them were clustered charged-to-alanine mutants in which clusters of charged residues mere changed to alanine residues, Two of them contained substitutions in Ser15 to either alanine or glutamic acid and three of the m had deletions at either the N-terminus or the C-terminus of the protein, In most of them, the catalytic activity correlated directly with their func tionality in glucose signalling, However, we found two mutants (Delta1-15 a nd Delta 476-486) that, having low catalytic activity, mere still fully fun ctional in glucose signalling, This may indicate that other factors and not just the catalytic activity of the enzyme may be important for the functio nality of the protein in glucose signalling, Copyright (C) 2001 John Wiley & Sons, Ltd.