Cysteine subcellular location

Little is known of the N-acetyl transferase(s) responsible for the acetylation of the S-substituted cysteine. It is found in the microsomes of the kidney and the liver, however, and is specific for acetyl CoA as the actyl donor. It is distinguished from other N-acetyltransferases by its substrate specificity and subcellular location. 

Attack points are metal ion centers and specific cysteine residues of proteins. The mechanisms by which cysteine nitrosylation regulates protein functions can be broadly described in allosteric terms similar to protein phosphorylation. Often, 02-mediated redox reactions cooperate in the allosteric control by NO of protein functions. S-nitrosylation of target proteins is a redox-based signal with exquisite specificity based on the selective modification of single cysteine residues. The selectivity of S-nitrosylation has been shown to be provided by both the subcellular distribution of NOS enzymes and the sequence context of cysteine residues in target proteins. Two nitrosylation motifs have been identified. In one motif, the target cysteine is located between an acidic and a basic amino acid, as revealed in either the primary sequence or the tertiary structure. In the other motif, the cysteine is contained in a hydrophobic region. 

Fig. 6. Subcellular location of the enzymes of cysteine and methionine synthesis in photosynthetic cells in C3 plants. The scheme incorporates the proposals of Wallsgrove et al. (1983) for the synthesis of phosphohomoserine and methionine and current understanding of the location of the enzymes of the sulfate assimilation pathway and of serine transacetylase. Abbreviations OAS, 0-acetylserine PHS, phosphohomoserine THF, tetrahydrofolate.

This activity is mainly located in particulate components of the primary subcellular fractions. About 35% of the enzyme activity is present in the crude mitochondrial fraction.Further subfractionation has shown that half of the cysteine sulphinate decarboxylase activity, present in this fraction, is localized In synaptosomes... 

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