Biology subjects

Grabinska, K. A.

Publications and source records attributed to Grabinska, K. A..

3 recordsLinked to original sources

bioRxiv2026

Dolichol biosynthesis in yeast traces the expanded reaction pathway of higher eukaryotes

The recent reassignment of Saccharomyces cerevisiae Dfg10 as a polyprenal reductase left two unresolved steps in yeast dolichol biosynthesis: the conversion of polyprenol to polyprenal and dolichal to dolichol. In humans, both of these steps are carried out by DHRSX, an enzyme with a unique dual specificity. We found that yeast Env9 catalyzes an NADPH-dependent reduction of dolichal to dolichol. However, in contrast to DHRSX, Env9 does not catalyze the conversion of polyprenol to polyprenal. Instead, our data indicates that this reaction is catalyzed by another yeast short chain oxidoreductase, Tda5. Thus, we provide evidence that the dual role of DHRSX in human dolichol synthesis is fulfilled by two dedicated yeast enzymes, Env9 and Tda5. Accordingly, deletion of ENV9 and TDA5 led to the accumulation of polyisoprenoid intermediates, transfer of immature lipid-linked oligosaccharides onto nascent proteins, and defective N-glycosylation. This is similar to what had been observed in DHRSX-deficient mammalian cells and yeast cells with DFG10 deleted. Furthermore, we discovered that loss of Dfg10 results in a deficiency of cell wall -mannan, revealing a critical sensitivity of yeast mannan biosynthesis to the quality of nascent N-linked glycans.

biochemistry↗

bioRxiv2023

Dual regulation of SLC25A39 by AFG3L2 and iron controls mitochondrial glutathione homeostasis

Organelle transporters define metabolic compartmentalization and how this metabolite transport process can be modulated is poorly explored. Here, we discovered that SLC25A39, a mitochondrial transporter critical for mitochondrial glutathione uptake, is a short-lived protein under dual regulation at the protein level. Co-immunoprecipitation mass spectrometry and CRISPR KO in cells identified that mitochondrial m-AAA protease AFG3L2 is responsible for degrading SLC25A39 through the matrix loop 1. SLC25A39 senses mitochondrial iron-sulfur cluster using four matrix cysteine residues and inhibits its degradation. SLC25A39 protein regulation is robust in developing and mature neurons. This dual transporter regulation, by protein quality control and metabolic sensing, allows modulating mitochondrial glutathione level in response to iron homeostasis, opening new avenues to explore regulation of metabolic compartmentalization. Neuronal SLC25A39 regulation connects mitochondrial protein quality control, glutathione and iron homeostasis, which were previously unrelated biochemical features in neurodegeneration.

cell biology↗

bioRxiv2017

Purification Of The Mammalian NgBR/hCIT cis-Prenyltransferase Complex: IdentificationOf A Conserved Carboxyterminal RxG Motif Crucial For Enzymatic Activity

Cis-Prenyltransferases (cisPTs) constitute a large family of enzymes conserved during evolution and present in all domains of life. In eukaryotes and archaea, cisPT is the first enzyme committed to the synthesis of dolichyl-phosphate (DolP). DolP is obligate lipid carrier in protein glycosylation reactions in mammals. The homodimeric bacterial enzyme, undecaprenyl diphosphate synthase (UPPS) generates 11 isoprene units and has been structurally and mechanistically characterized in great detail. Recently our group discovered that unlike UPPS, mammalian cisPT is a heteromer consisting of NgBR (NUS1) and hCIT (DHDDS) subunits and this composition has been confirmed in plants and fungal cisPTs. Here, we establish the first purification system for heteromeric cisPT and show that both NgBR and hCIT subunits function in catalysis and substrate binding. Finally, we identified a critical RxG sequence in the C-terminal tail of NgBR that is conserved and essential for enzyme activity across phyla.

biochemistry↗