A nano switch mechanism for the redox-responsive sulfotransferase
Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan.Biochemical pharmacology (Impact Factor: 5.01). 04/2012; 84(2):224-31. DOI: 10.1016/j.bcp.2012.04.003
Cellular redox signaling is important in diverse physiological and pathological processes. The activity of rat phenol sulfotransferase (rSULT1A1), which is important for the metabolism of hormone and drug, is subjected to redox regulation. Two cysteines, Cys232 and Cys66, nanometer away from each other and from the enzyme active site were proposed to form disulfide bond to regulate the activity of rSULT1A1. A nano switch, composed of a flexible loop from amino acid residues 59-70, explained how this long distance interaction between two cysteines can be achieved. The enzyme properties were investigated through site-directed muatagnesis, circular dichroism, enzyme kinetics and homologous modeling of the rSULT1A1 structures. We proposed that the formation of disulfide bond between Cys232 and Cys66 induced conformational changes of sulfotransferase, then in turn affected its nucleotide binding and enzyme activity. This discovery was extended to understand the possible redox regulation of other sulfotransferases from different organisms. The redox switch can be created in other redox-insensitive sulfotransferases, such as human phenol sulfotransferase (hSULT1A1) and human alcohol sulfotransferase (hSULT2A1), to produce mutant enzymes with redox regulation capacity. This study strongly suggested that redox regulation of drug and hormone metabolism can be significantly varied even though the sequence and structure of SULT1A1 of human and rat have a high degree of homology.
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ABSTRACT: Cytosolic sulfotransferases (SULTs), one of the vital enzymes of detoxication, catalyze the sulfation of native and exogenous hydrophobic molecules. Xenobiotic accumulation can induce a variety of diseases, including cancers. Sulfation facilitates the solubilization and removal of xenobiotics. However, sulfation may activate the pharmacological activities of xenobiotics. The purpose of this review was to correlate the sequence, structure and function of SULTs. We focused on understanding the sulfation mechanisms of SULT through its sequence variation. We selectively reviewed SULT drug substrates, explained the enzyme-catalyzed sulfation reaction and its kinetic mechanisms, and the effect of amino acid sequence variation, such as single-nucleotide polymorphism, on the enzyme function. A wealth of information is available in the literature for understanding the detailed mechanisms underlying xenobiotic sulfation. We reviewed information regarding the sequence, structure and reaction mechanism of SULTs and explained how SULT activities altered. In addition to revealing the SULT kinetics, the mRNA expression of specific SULTs in tissues that revealed their distribution in tissues also affects overall SULT activities. Understanding of the structure-function relationship and the reaction mechanism of SULTs is valuable for understanding, preventing and treating diseases.
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