Glucose-induced inactivation of isocitrate lyase in Saccharomyces cerevisiae is mediated by an internal decapeptide sequence

In this work we have investigated the role of specific peptide sequences for glucose-inactivation of the yeast isocitrate lyase. Thus, different fragments of the ICL1 coding region were fused to the lacZ gene of E. coli to provide a reporter construction. Determinations of β-galactosidase activities indicated that the decapeptide sequence KTKRNYSARD, located between amino acid residues 37 and 46 of isocitrate lyase, is important for glucose induced proteolytic inactivation. Further experimental evidence was provided by insertion of this sequence into a glucokinase-β-alactosidase fusion protein, which is not sensitive to glucose regulation. The decapeptide inserted conferred glucose inactivation to this construct, confirming that it is both necessary and sufficient as a signal.