TY - JOUR
T1 - Sulfotransferase 1A1 Substrate Selectivity
T2 - A Molecular Clamp Mechanism
AU - Cook, Ian
AU - Wang, Ting
AU - Leyh, Thomas S.
N1 - Publisher Copyright:
© 2015 American Chemical Society.
PY - 2015/10/6
Y1 - 2015/10/6
N2 - The human cytosolic sulfotransferases (SULTs) regulate hundreds, perhaps thousands, of small molecule metabolites and xenobiotics via transfer of a sulfuryl moiety (-SO3) from PAPS (3′-phosphoadenosine 5′-phosphosulfate) to the hydroxyls and primary amines of the recipients. In liver, where it is abundant, SULT1A1 engages in modifying metabolites and neutralizing toxins. The specificity of 1A1 is the broadest of any SULT, and understanding its selectivity is fundamental to understanding its biology. Here, for the first time, we show that SULT1A1 substrates separate naturally into two classes: those whose affinities are either enhanced ∼20-fold (positive synergy) or unaffected (neutral synergy) by the presence of a saturating nucleotide. kcat for the positive-synergy substrates is shown to be ∼100-fold greater than that of neutral-synergy compounds; consequently, the catalytic efficiency (kcat/Km) is approximately 3 orders of magnitude greater for the positive-synergy species. All-atom dynamics modeling suggests a molecular mechanism for these observations in which the binding of only positive-synergy compounds causes two phenylalanine residues (F81 and 84) to reposition and "sandwich" the phenolic moiety of the substrates, thus enhancing substrate affinity and positioning the nucleophilic oxygen for attack. Molecular dynamics movies reveal that the neutral-synergy compounds "wander" about the active site, infrequently achieving a reactive position. In-depth analysis of select point mutants strongly supports the model and provides an intimate view of the interdependent catalytic functions of subsections of the active site.
AB - The human cytosolic sulfotransferases (SULTs) regulate hundreds, perhaps thousands, of small molecule metabolites and xenobiotics via transfer of a sulfuryl moiety (-SO3) from PAPS (3′-phosphoadenosine 5′-phosphosulfate) to the hydroxyls and primary amines of the recipients. In liver, where it is abundant, SULT1A1 engages in modifying metabolites and neutralizing toxins. The specificity of 1A1 is the broadest of any SULT, and understanding its selectivity is fundamental to understanding its biology. Here, for the first time, we show that SULT1A1 substrates separate naturally into two classes: those whose affinities are either enhanced ∼20-fold (positive synergy) or unaffected (neutral synergy) by the presence of a saturating nucleotide. kcat for the positive-synergy substrates is shown to be ∼100-fold greater than that of neutral-synergy compounds; consequently, the catalytic efficiency (kcat/Km) is approximately 3 orders of magnitude greater for the positive-synergy species. All-atom dynamics modeling suggests a molecular mechanism for these observations in which the binding of only positive-synergy compounds causes two phenylalanine residues (F81 and 84) to reposition and "sandwich" the phenolic moiety of the substrates, thus enhancing substrate affinity and positioning the nucleophilic oxygen for attack. Molecular dynamics movies reveal that the neutral-synergy compounds "wander" about the active site, infrequently achieving a reactive position. In-depth analysis of select point mutants strongly supports the model and provides an intimate view of the interdependent catalytic functions of subsections of the active site.
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U2 - 10.1021/acs.biochem.5b00406
DO - 10.1021/acs.biochem.5b00406
M3 - Article
C2 - 26340710
AN - SCOPUS:84942845696
SN - 0006-2960
VL - 54
SP - 6114
EP - 6122
JO - Biochemistry
JF - Biochemistry
IS - 39
ER -