Channeling in sulfate activating complexes

Meihao Sun, Thomas S. Leyh

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

The synthesis of activated sulfate (adenosine 5′-phosphosulfate, APS) and inorganic pyrophosphate from ATP and SO4 is remarkably unfavorable: Keq ∼ 10-8 under presumed, near-physiological conditions. Consequently, ATP sulfurylases, which catalyze APS synthesis, suffer ∼108-fold losses in catalytic efficiency in the forward (APS-synthesis) versus reverse reaction. Losses of this magnitude place this catalyst at risk of being unable to supply its nutrients to the cell in a timely fashion. ATP sulfurylase domains are often embedded in multifunctional complexes that are capable of also catalyzing the second of two steps in the sulfate activation pathway: the phosphorylation of APS to produce PAPS (3′-phosphoadenosine 5′-phosphosulfate). The colocalization of these activities in a single scaffold suggests that evolution might have worked around the inefficiency problem by fashioning a system capable of transferring APS directly between the active sites of the complex, thereby avoiding the solution-phase energetics. For these reasons, representatives from each of the three types of sulfate activating complex (SAC) [Homo sapiens (type I); Mycobacterium tuberculosis (type II); and Rhodobacter sphaeroides (type III)] were tested for the ability to channel APS. A channeling assay that optically detects solution-phase APS was devised with APS reductase from M. tuberculosis, a previously uncharacterized enzyme. Channeling was not detected in two of the three types of SAC; however, the type III SAC channels with high efficiency. Structural models of type HI reveal a 75 Å-long channel that interconnects active-site pairs in the complex and that opens and closes in response to occupancy of those sites.

Original languageEnglish (US)
Pages (from-to)11304-11311
Number of pages8
JournalBiochemistry
Volume45
Issue number38
DOIs
StatePublished - Sep 26 2006

Fingerprint

Adenosine Phosphosulfate
Sulfates
Mycobacterium tuberculosis
Catalytic Domain
Sulfate Adenylyltransferase
Adenosine Triphosphate
Phosphoadenosine Phosphosulfate
Rhodobacter sphaeroides
Phosphorylation
Structural Models
Scaffolds
Nutrients
Assays
Chemical activation
Food
Catalysts

ASJC Scopus subject areas

  • Biochemistry

Cite this

Channeling in sulfate activating complexes. / Sun, Meihao; Leyh, Thomas S.

In: Biochemistry, Vol. 45, No. 38, 26.09.2006, p. 11304-11311.

Research output: Contribution to journalArticle

Sun, Meihao ; Leyh, Thomas S. / Channeling in sulfate activating complexes. In: Biochemistry. 2006 ; Vol. 45, No. 38. pp. 11304-11311.
@article{f0d88899d0f549ffbcf24588c5258623,
title = "Channeling in sulfate activating complexes",
abstract = "The synthesis of activated sulfate (adenosine 5′-phosphosulfate, APS) and inorganic pyrophosphate from ATP and SO4 is remarkably unfavorable: Keq ∼ 10-8 under presumed, near-physiological conditions. Consequently, ATP sulfurylases, which catalyze APS synthesis, suffer ∼108-fold losses in catalytic efficiency in the forward (APS-synthesis) versus reverse reaction. Losses of this magnitude place this catalyst at risk of being unable to supply its nutrients to the cell in a timely fashion. ATP sulfurylase domains are often embedded in multifunctional complexes that are capable of also catalyzing the second of two steps in the sulfate activation pathway: the phosphorylation of APS to produce PAPS (3′-phosphoadenosine 5′-phosphosulfate). The colocalization of these activities in a single scaffold suggests that evolution might have worked around the inefficiency problem by fashioning a system capable of transferring APS directly between the active sites of the complex, thereby avoiding the solution-phase energetics. For these reasons, representatives from each of the three types of sulfate activating complex (SAC) [Homo sapiens (type I); Mycobacterium tuberculosis (type II); and Rhodobacter sphaeroides (type III)] were tested for the ability to channel APS. A channeling assay that optically detects solution-phase APS was devised with APS reductase from M. tuberculosis, a previously uncharacterized enzyme. Channeling was not detected in two of the three types of SAC; however, the type III SAC channels with high efficiency. Structural models of type HI reveal a 75 {\AA}-long channel that interconnects active-site pairs in the complex and that opens and closes in response to occupancy of those sites.",
author = "Meihao Sun and Leyh, {Thomas S.}",
year = "2006",
month = "9",
day = "26",
doi = "10.1021/bi060421e",
language = "English (US)",
volume = "45",
pages = "11304--11311",
journal = "Biochemistry",
issn = "0006-2960",
publisher = "American Chemical Society",
number = "38",

}

TY - JOUR

T1 - Channeling in sulfate activating complexes

AU - Sun, Meihao

AU - Leyh, Thomas S.

PY - 2006/9/26

Y1 - 2006/9/26

N2 - The synthesis of activated sulfate (adenosine 5′-phosphosulfate, APS) and inorganic pyrophosphate from ATP and SO4 is remarkably unfavorable: Keq ∼ 10-8 under presumed, near-physiological conditions. Consequently, ATP sulfurylases, which catalyze APS synthesis, suffer ∼108-fold losses in catalytic efficiency in the forward (APS-synthesis) versus reverse reaction. Losses of this magnitude place this catalyst at risk of being unable to supply its nutrients to the cell in a timely fashion. ATP sulfurylase domains are often embedded in multifunctional complexes that are capable of also catalyzing the second of two steps in the sulfate activation pathway: the phosphorylation of APS to produce PAPS (3′-phosphoadenosine 5′-phosphosulfate). The colocalization of these activities in a single scaffold suggests that evolution might have worked around the inefficiency problem by fashioning a system capable of transferring APS directly between the active sites of the complex, thereby avoiding the solution-phase energetics. For these reasons, representatives from each of the three types of sulfate activating complex (SAC) [Homo sapiens (type I); Mycobacterium tuberculosis (type II); and Rhodobacter sphaeroides (type III)] were tested for the ability to channel APS. A channeling assay that optically detects solution-phase APS was devised with APS reductase from M. tuberculosis, a previously uncharacterized enzyme. Channeling was not detected in two of the three types of SAC; however, the type III SAC channels with high efficiency. Structural models of type HI reveal a 75 Å-long channel that interconnects active-site pairs in the complex and that opens and closes in response to occupancy of those sites.

AB - The synthesis of activated sulfate (adenosine 5′-phosphosulfate, APS) and inorganic pyrophosphate from ATP and SO4 is remarkably unfavorable: Keq ∼ 10-8 under presumed, near-physiological conditions. Consequently, ATP sulfurylases, which catalyze APS synthesis, suffer ∼108-fold losses in catalytic efficiency in the forward (APS-synthesis) versus reverse reaction. Losses of this magnitude place this catalyst at risk of being unable to supply its nutrients to the cell in a timely fashion. ATP sulfurylase domains are often embedded in multifunctional complexes that are capable of also catalyzing the second of two steps in the sulfate activation pathway: the phosphorylation of APS to produce PAPS (3′-phosphoadenosine 5′-phosphosulfate). The colocalization of these activities in a single scaffold suggests that evolution might have worked around the inefficiency problem by fashioning a system capable of transferring APS directly between the active sites of the complex, thereby avoiding the solution-phase energetics. For these reasons, representatives from each of the three types of sulfate activating complex (SAC) [Homo sapiens (type I); Mycobacterium tuberculosis (type II); and Rhodobacter sphaeroides (type III)] were tested for the ability to channel APS. A channeling assay that optically detects solution-phase APS was devised with APS reductase from M. tuberculosis, a previously uncharacterized enzyme. Channeling was not detected in two of the three types of SAC; however, the type III SAC channels with high efficiency. Structural models of type HI reveal a 75 Å-long channel that interconnects active-site pairs in the complex and that opens and closes in response to occupancy of those sites.

UR - http://www.scopus.com/inward/record.url?scp=33748991984&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33748991984&partnerID=8YFLogxK

U2 - 10.1021/bi060421e

DO - 10.1021/bi060421e

M3 - Article

VL - 45

SP - 11304

EP - 11311

JO - Biochemistry

JF - Biochemistry

SN - 0006-2960

IS - 38

ER -