Ca2+/calmodulin-binding proteins in yeast. Catabolite repression and induction by carbon sources

Area of Science:

• * Molecular Biology
• * Yeast Genetics
• * Protein Biochemistry

Background:

• * Calmodulin is a key calcium-binding protein regulating cellular processes in eukaryotes.
• * Understanding calmodulin-binding proteins in yeast (Saccharomyces carlsbergensis) provides insights into cellular signaling and metabolism.
• * Carbon source availability significantly impacts yeast gene expression and protein profiles.

Purpose of the Study:

• * To identify and characterize soluble calmodulin-binding proteins in Saccharomyces carlsbergensis.
• * To investigate the influence of different carbon sources (glucose, maltose, galactose) on the expression of these proteins.
• * To determine the role of calcium/calmodulin in the phosphorylation of these identified proteins.

Main Methods:

• * Affinity chromatography using calmodulin as bait to isolate binding proteins.
• * Overlay techniques to confirm protein-calmodulin interactions.
• * Analysis of protein phosphorylation via Ca2+/calmodulin-dependent [gamma-32P] incorporation.

Main Results:

• * Multiple calmodulin-binding polypeptides were identified across different growth conditions.
• * Specific polypeptides (115, 67, 45 kDa) showed patterns consistent with catabolite repression.
• * Unique polypeptides were observed on maltose (195, 22 kDa) and galactose (88 kDa) media.
• * Eight calmodulin-binding proteins were phosphorylated in a Ca2+/calmodulin-dependent manner.
• * Heat treatment significantly reduced Ca2+/calmodulin-dependent phosphorylation.

Conclusions:

• * Saccharomyces carlsbergensis possesses a diverse set of calmodulin-binding proteins.
• * The expression of certain calmodulin-binding proteins is regulated by carbon source and potentially catabolite repression.
• * Calcium/calmodulin signaling plays a role in the phosphorylation of specific yeast proteins, impacting cellular responses.