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Dimeric human sulfotransferase 1B1 displays cofactor-dependent subunit communication.

Tibbs ZE, Falany CN - Pharmacol Res Perspect (2015)

Bottom Line: While SULT dimerization is highly conserved, the necessity for the interaction has not been established.The results suggest the dimer subunits may possess the capability of communicating with one another in a manner dependent on the presence of the cofactor.These results suggest SULT dimerization may be important in maintaining cofactor binding/release properties of SULTs and provide hypothetical explanations for SULT half-site reactivity and substrate inhibition, which can be analyzed in vitro.

View Article: PubMed Central - PubMed

Affiliation: The Department of Pharmacology and Toxicology, The University of Alabama at Birmingham Birmingham, Alabama, 35294-0019.

ABSTRACT
The cytosolic sulfotransferases (SULTs) are dimeric enzymes that catalyze the transformation of hydrophobic drugs and hormones into hydrophilic sulfate esters thereby providing the body with an important pathway for regulating small molecule activity and excretion. While SULT dimerization is highly conserved, the necessity for the interaction has not been established. To perform its function, a SULT must efficiently bind the universal sulfate donor, 3'-phosphoadenosine-5'-phosphosulfate (PAPS), and release the byproduct, 3', 5'-diphosphoadenosine (PAP), following catalysis. We hypothesize this efficient binding and release of PAPS/PAP may be connected to SULT dimerization. To allow for the visualization of dynamic protein interactions critical for addressing this hypothesis and to generate kinetically testable hypotheses, molecular dynamic simulations (MDS) of hSULT1B1 were performed with PAPS and PAP bound to each dimer subunit in various combinations. The results suggest the dimer subunits may possess the capability of communicating with one another in a manner dependent on the presence of the cofactor. PAP or PAPS binding to a single side of the dimer results in decreased backbone flexibility of both the bound and unbound subunits, implying the dimer subunits may not act independently. Further, binding of PAP to one subunit of the dimer and PAPS to the other caused increased flexibility in the subunit bound to the inactive cofactor (PAP). These results suggest SULT dimerization may be important in maintaining cofactor binding/release properties of SULTs and provide hypothetical explanations for SULT half-site reactivity and substrate inhibition, which can be analyzed in vitro.

No MeSH data available.


Related in: MedlinePlus

Visual indication of the broken hinge region. Shortly following a shift in the binding position of PAP (magenta sticks), a key hydrogen bond (dashed line) between Met146 and Asp250 (yellow tube) was broken, allowing Loop 3 (green) to be highly mobile. The shift in PAP appears to be translated to Loop 3 primarily by an interaction with a single residue (R258).
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fig10: Visual indication of the broken hinge region. Shortly following a shift in the binding position of PAP (magenta sticks), a key hydrogen bond (dashed line) between Met146 and Asp250 (yellow tube) was broken, allowing Loop 3 (green) to be highly mobile. The shift in PAP appears to be translated to Loop 3 primarily by an interaction with a single residue (R258).

Mentions: The shift in PAP orientation directly precedes the unhinging of Loop 3 (Fig.10). Loop 3’s interaction with the cofactor (PAP) is mediated by a single residue, R258, that is conserved across all SULTs. R258 directly interacts with the 3′-phosphate of PAP, the portion of PAP that underwent the largest shift in orientation. R258 maintains its interaction with the 3′-phosphate of PAP even after the molecule shifted (Fig.9).


Dimeric human sulfotransferase 1B1 displays cofactor-dependent subunit communication.

Tibbs ZE, Falany CN - Pharmacol Res Perspect (2015)

Visual indication of the broken hinge region. Shortly following a shift in the binding position of PAP (magenta sticks), a key hydrogen bond (dashed line) between Met146 and Asp250 (yellow tube) was broken, allowing Loop 3 (green) to be highly mobile. The shift in PAP appears to be translated to Loop 3 primarily by an interaction with a single residue (R258).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4492763&req=5

fig10: Visual indication of the broken hinge region. Shortly following a shift in the binding position of PAP (magenta sticks), a key hydrogen bond (dashed line) between Met146 and Asp250 (yellow tube) was broken, allowing Loop 3 (green) to be highly mobile. The shift in PAP appears to be translated to Loop 3 primarily by an interaction with a single residue (R258).
Mentions: The shift in PAP orientation directly precedes the unhinging of Loop 3 (Fig.10). Loop 3’s interaction with the cofactor (PAP) is mediated by a single residue, R258, that is conserved across all SULTs. R258 directly interacts with the 3′-phosphate of PAP, the portion of PAP that underwent the largest shift in orientation. R258 maintains its interaction with the 3′-phosphate of PAP even after the molecule shifted (Fig.9).

Bottom Line: While SULT dimerization is highly conserved, the necessity for the interaction has not been established.The results suggest the dimer subunits may possess the capability of communicating with one another in a manner dependent on the presence of the cofactor.These results suggest SULT dimerization may be important in maintaining cofactor binding/release properties of SULTs and provide hypothetical explanations for SULT half-site reactivity and substrate inhibition, which can be analyzed in vitro.

View Article: PubMed Central - PubMed

Affiliation: The Department of Pharmacology and Toxicology, The University of Alabama at Birmingham Birmingham, Alabama, 35294-0019.

ABSTRACT
The cytosolic sulfotransferases (SULTs) are dimeric enzymes that catalyze the transformation of hydrophobic drugs and hormones into hydrophilic sulfate esters thereby providing the body with an important pathway for regulating small molecule activity and excretion. While SULT dimerization is highly conserved, the necessity for the interaction has not been established. To perform its function, a SULT must efficiently bind the universal sulfate donor, 3'-phosphoadenosine-5'-phosphosulfate (PAPS), and release the byproduct, 3', 5'-diphosphoadenosine (PAP), following catalysis. We hypothesize this efficient binding and release of PAPS/PAP may be connected to SULT dimerization. To allow for the visualization of dynamic protein interactions critical for addressing this hypothesis and to generate kinetically testable hypotheses, molecular dynamic simulations (MDS) of hSULT1B1 were performed with PAPS and PAP bound to each dimer subunit in various combinations. The results suggest the dimer subunits may possess the capability of communicating with one another in a manner dependent on the presence of the cofactor. PAP or PAPS binding to a single side of the dimer results in decreased backbone flexibility of both the bound and unbound subunits, implying the dimer subunits may not act independently. Further, binding of PAP to one subunit of the dimer and PAPS to the other caused increased flexibility in the subunit bound to the inactive cofactor (PAP). These results suggest SULT dimerization may be important in maintaining cofactor binding/release properties of SULTs and provide hypothetical explanations for SULT half-site reactivity and substrate inhibition, which can be analyzed in vitro.

No MeSH data available.


Related in: MedlinePlus