The ICL1 gene from Saccharomyces cerevisiae

Area of Science:

• Molecular biology
• Yeast genetics
• Metabolic pathways

Background:

• The glyoxylate cycle is vital for Saccharomyces cerevisiae to metabolize C2 compounds.
• Isocitrate lyase is a key enzyme in this essential metabolic pathway.

Purpose of the Study:

• To identify and characterize the structural gene (ICL1) encoding isocitrate lyase in Saccharomyces cerevisiae.
• To understand the role of ICL1 in yeast growth on ethanol.

Main Methods:

• Screening for yeast mutants unable to grow on ethanol.
• Genetic and biochemical analysis to identify the defective gene.
• Gene isolation, DNA sequencing, and construction of deletion-substitution mutants.
• Bioinformatic analysis of the deduced protein sequence.

Main Results:

• Mutants lacking isocitrate lyase activity were identified and linked to the ICL1 gene.
• The ICL1 gene was isolated and localized to a 3.1-kb DNA fragment.
• A deletion-substitution mutant confirmed the gene's essential role in growth on ethanol.
• Sequencing revealed an open reading frame encoding a 557-amino acid protein with similarities to other isocitrate lyases.
• Two potential phosphorylation sites were identified, suggesting regulation by carbon catabolite inactivation.

Conclusions:

• The ICL1 gene is essential for isocitrate lyase activity and growth on ethanol in Saccharomyces cerevisiae.
• The deduced protein sequence provides insights into isocitrate lyase function and regulation.
• Potential phosphorylation sites suggest a mechanism for enzyme regulation via carbon catabolite inactivation.