Cysteine, a thiol containing amino acid synthesized via the transsulfuration pathway is a rate limiting precursor for glutathione synthesis and is also utilized for protein synthesis. Among the biological thiols elevated levels of homocysteine is known to be associated with various diseases and is considered to be an independent risk factor for cardiovascular disease. Recent evidences actually support this fact and it has been shown that cysteine induced growth defect in yeast was more severe than homocysteine. Reports also suggest that elevated levels of cysteine may be associated with cardiovascular disease. Using Yeast as a model system in this study we have tried to figure out the mechanism of cysteine induced toxicity. To characterize the cellular response in presence of high level of cysteine we have performed a quantitative proteomics experiment and found several differentially expressed proteins in presence of high level of cysteine which includes aminoacid metabolic proteins, glycolytic – TCA cycle proteins, ribosomal proteins. Even after genomewide mutant screening we came to know that Ncl1 (SAM dependent t-RNA methyl transferase) plays a crucial role in Cysteine toxicity. ∆ncl1 is much more sensitive towards cysteine and it plays a crucial role in protein biosynthesis and energy metabolism.Intracellular aminoacid measurement by using o-phtalaldehyde reveals that cysteine causes aminoacid imbalance in the cells and by using s35 labeled methionine we also found that cysteine induces translational arrest. Further we have found that supplementation of high levels of leucine and pyruvate can rescue cysteine induced toxicity.