Related Experiment Video
Updated: Jun 18, 2026

Genome-wide Protein-protein Interaction Screening by Protein-fragment Complementation Assay (PCA) in Living Cells
Published on: March 3, 2015
Moonlighting proteins Hal3 and Vhs3 form a heteromeric PPCDC with Ykl088w in yeast CoA biosynthesis
Amparo Ruiz1, Asier González, Ivan Muñoz
1Departament de Bioquimica i Biologia Molecular, Universitat Autònoma de Barcelona, Spain.
Abstract:
Unlike most other organisms, the essential five-step coenzyme A biosynthetic pathway has not been fully resolved in yeast. Specifically, the genes encoding the phosphopantothenoylcysteine decarboxylase (PPCDC) activity still remain unidentified. Sequence homology analyses suggest three candidates-Ykl088w, Hal3 and Vhs3-as putative PPCDC enzymes in Saccharomyces cerevisiae. Notably, Hal3 and Vhs3 have been characterized as negative regulatory subunits of the Ppz1 protein phosphatase. Here we show that YKL088w does not encode a third Ppz1 regulatory subunit, and that the essential roles of Ykl088w and the Hal3 and Vhs3 pair are complementary, cannot be interchanged and can be attributed to PPCDC-related functions. We demonstrate that while known eukaryotic PPCDCs are homotrimers, the active yeast enzyme is a heterotrimer that consists of Ykl088w and Hal3/Vhs3 monomers that separately provides two essential catalytic residues. Our results unveil Hal3 and Vhs3 as moonlighting proteins involved in both CoA biosynthesis and protein phosphatase regulation.
Related Concept Videos
Yeast Signaling
Protein Complexes with Interchangeable Parts
The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order to...
Amino Acid Biosynthetic Pathways
Covalently Linked Protein Regulators
These groups modify specific amino acids in a protein.
Covalently Linked Protein Regulators
These groups modify specific amino acids in a protein.
Mitochondrial Protein Sorting
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...

