Fig. 4: Metabolic defects in yeast strains harboring cab1 mutations.

a PanK activities in the cab1∆ strains harboring various CAB1 mutations. Cell free extracts of yeast cab1 mutants were used to measure the endogenous PA utilization of cab1∆ + CAB1, cab1∆ + cab1^G351S, cab1∆ + cab1^G351S + CAB1, cab1∆ + cab1^S158A, cab1∆ + cab1^S158A + CAB1, and cab1∆ + cab1^N290I, cab1∆ + cab1^N290I + CAB1 strains using D-[1-¹⁴C] pantothenate as a substrate for 10 min at 30 °C. Each data plot represents the average of three biological samples with the corresponding standard deviation (±SD). b Cellular levels of CoA in cab1∆ strains. CoA levels were measured using metabolite extracts from the yeast strains mentioned above grown in the presence of 0.2 µM PA. Each data plot represents the average of three biological samples with the corresponding standard deviation (±SD). c Cysteine cellular levels of cab1∆ strains harboring various CAB1 mutations. Cellular cysteine levels were measured using the metabolite extracts from the yeast strain mentioned above grown in the presence of 0.2 µM PA. For these assays, t-test was done per each group compared to the parent CAB1 wild-type strain (p = 0.05). Each data plot represents the average of three biological samples with the corresponding standard deviation (±SD). d Schematic of the connection between the PCA pathway and the SUL/MET pathways. Transcription of the SUL/MET genes, responsible for synthesizing the crucial sulfur-containing amino acids methionine and cysteine, is mediated by the transcription factor Met4. This regulatory process is sensitive to changes in cellular cysteine levels. When cysteine levels increase, Met4 undergoes ubiquitination by the ubiquitin ligase Met30, leading to Met4’s inactivation and subsequent repression of the SUL/MET genes. e RNA-Seq analysis for cysteine and sulfur homeostasis expressed in cab1∆ strains. Expression values are TMM normalized and adjusted p-values (padj) were calculated using the Benjamini-Hochberg method. The data represent the average of three biological samples. The illustrated volcano plot depicts log2-fold change values for the mutants, cab1∆ + cab1^G351S, cab1∆ + cab1^N290I, and cab1∆ + cab1^S158A in gray, cyan, and pink, respectively, against cab1∆ + CAB1 WT, plotted against the negative logarithm of the padj values. The gene list with annotations shown in Table S1.