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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

Change in PAP orientation within the hSULT1B1 active site. (A) The RMSD of PAP in simulation [6] (white circle) indicates time-point at which the structural shift occurred (22.1 nsec). The RMSD of PAP in Chain B of simulation [5] is included for reference (black triangle). (B) The average PAP orientation during the first 22.1 nsec is illustrated in green while the average PAP orientation for the remainder of the simulation is illustrated in magenta. (C) Each atom of the PAP structure is colored according to its RMSD value. Areas in red (e.g., the 3′ phosphate) display greatest divergence from the original conformation, while areas in blue remain unchanged.
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fig09: Change in PAP orientation within the hSULT1B1 active site. (A) The RMSD of PAP in simulation [6] (white circle) indicates time-point at which the structural shift occurred (22.1 nsec). The RMSD of PAP in Chain B of simulation [5] is included for reference (black triangle). (B) The average PAP orientation during the first 22.1 nsec is illustrated in green while the average PAP orientation for the remainder of the simulation is illustrated in magenta. (C) Each atom of the PAP structure is colored according to its RMSD value. Areas in red (e.g., the 3′ phosphate) display greatest divergence from the original conformation, while areas in blue remain unchanged.

Mentions: Analysis of simulation [6] provided visual indication that PAP underwent a structural shift during the simulation. Therefore, the RMSD was calculated for the inactive cofactor. RMSD calculations show the shift occurs 22.1 nsec after the system reached equilibration (Fig.9).


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

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

Change in PAP orientation within the hSULT1B1 active site. (A) The RMSD of PAP in simulation [6] (white circle) indicates time-point at which the structural shift occurred (22.1 nsec). The RMSD of PAP in Chain B of simulation [5] is included for reference (black triangle). (B) The average PAP orientation during the first 22.1 nsec is illustrated in green while the average PAP orientation for the remainder of the simulation is illustrated in magenta. (C) Each atom of the PAP structure is colored according to its RMSD value. Areas in red (e.g., the 3′ phosphate) display greatest divergence from the original conformation, while areas in blue remain unchanged.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig09: Change in PAP orientation within the hSULT1B1 active site. (A) The RMSD of PAP in simulation [6] (white circle) indicates time-point at which the structural shift occurred (22.1 nsec). The RMSD of PAP in Chain B of simulation [5] is included for reference (black triangle). (B) The average PAP orientation during the first 22.1 nsec is illustrated in green while the average PAP orientation for the remainder of the simulation is illustrated in magenta. (C) Each atom of the PAP structure is colored according to its RMSD value. Areas in red (e.g., the 3′ phosphate) display greatest divergence from the original conformation, while areas in blue remain unchanged.
Mentions: Analysis of simulation [6] provided visual indication that PAP underwent a structural shift during the simulation. Therefore, the RMSD was calculated for the inactive cofactor. RMSD calculations show the shift occurs 22.1 nsec after the system reached equilibration (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