Pulse Radiolysis Studies of Temperature Dependent Electron Transfers among Redox Centers in ba(3)-Cytochrome c Oxidase from Thermus thermophilus: Comparison of A- and B-Type Enzymes

Ole Farver; Scot Wherland; William E Antholine; Gregory J Gemmen; Ying Chen; Israel Pecht; James A Fee

doi:10.1021/bi100548n

Pulse Radiolysis Studies of Temperature Dependent Electron Transfers among Redox Centers in ba(3)-Cytochrome c Oxidase from Thermus thermophilus: Comparison of A- and B-Type Enzymes

Ole Farver, Scot Wherland, William E Antholine, Gregory J Gemmen, Ying Chen, Israel Pecht, James A Fee

Abstract

The functioning of cytochrome c oxidases involves orchestration of long-range electron transfer (ET) events among the four redox active metal centers. We report the temperature dependence of electron transfer from the Cu(A)(r) site to the low-spin heme-(a)b(o) site, i.e., Cu(A)(r) + heme-a(b)(o) → Cu(A)(o) + heme-a(b)(r) in three structurally characterized enzymes: A-type aa(3) from Paracoccus denitrificans (PDB code 3HB3 ) and bovine heart tissue (PDB code 2ZXW ), and the B-type ba(3) from T. thermophilus (PDB codes 1EHK and 1XME ). k,T data sets were obtained with the use of pulse radiolysis as described previously. Semiclassical Marcus theory revealed that λ varies from 0.74 to 1.1 eV, H(ab), varies from ∼2 × 10(-5) eV (0.16 cm(-1)) to ∼24 × 10(-5) eV (1.9 cm(-1)), and βD varies from 9.3 to 13.9. These parameters are consistent with diabatic electron tunneling. The II-Asp111Asn Cu(A) mutation in cytochrome ba(3) had no effect on the rate of this reaction whereas the II-Met160Leu Cu(A)-mutation was slower by an amount corresponding to a decreased driving force of ∼0.06 eV. The structures support the presence of a common, electron-conducting "wire" between Cu(A) and heme-a(b). The transfer of an electron from the low-spin heme to the high-spin heme, i.e., heme-a(b)(r) + heme-a(3)(o) → heme-a(b)(o) + heme-a(3)(r), was not observed with the A-type enzymes in our experiments but was observed with the Thermus ba(3); its Marcus parameters are λ = 1.5 eV, H(ab) = 26.6 × 10(-5) eV (2.14 cm(-1)), and βD = 9.35, consistent also with diabatic electron tunneling between the two hemes. The II-Glu15Ala mutation of the K-channel structure, ∼24 Å between its CA and Fe-a(3), was found to completely block heme-b(r) to heme-a(3)(o) electron transfer. A structural mechanism is suggested to explain these observations.

Original language	English
Journal	Biochemistry
ISSN	0006-2960
DOIs	https://doi.org/10.1021/bi100548n
Publication status	Published - 15 Nov 2022

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10.1021/bi100548n

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@article{321012b0e8304b78af1b8293c2e179ba,

title = "Pulse Radiolysis Studies of Temperature Dependent Electron Transfers among Redox Centers in ba(3)-Cytochrome c Oxidase from Thermus thermophilus: Comparison of A- and B-Type Enzymes",

abstract = "The functioning of cytochrome c oxidases involves orchestration of long-range electron transfer (ET) events among the four redox active metal centers. We report the temperature dependence of electron transfer from the Cu(A)(r) site to the low-spin heme-(a)b(o) site, i.e., Cu(A)(r) + heme-a(b)(o) → Cu(A)(o) + heme-a(b)(r) in three structurally characterized enzymes: A-type aa(3) from Paracoccus denitrificans (PDB code 3HB3 ) and bovine heart tissue (PDB code 2ZXW ), and the B-type ba(3) from T. thermophilus (PDB codes 1EHK and 1XME ). k,T data sets were obtained with the use of pulse radiolysis as described previously. Semiclassical Marcus theory revealed that λ varies from 0.74 to 1.1 eV, H(ab), varies from ∼2 × 10(-5) eV (0.16 cm(-1)) to ∼24 × 10(-5) eV (1.9 cm(-1)), and βD varies from 9.3 to 13.9. These parameters are consistent with diabatic electron tunneling. The II-Asp111Asn Cu(A) mutation in cytochrome ba(3) had no effect on the rate of this reaction whereas the II-Met160Leu Cu(A)-mutation was slower by an amount corresponding to a decreased driving force of ∼0.06 eV. The structures support the presence of a common, electron-conducting {"}wire{"} between Cu(A) and heme-a(b). The transfer of an electron from the low-spin heme to the high-spin heme, i.e., heme-a(b)(r) + heme-a(3)(o) → heme-a(b)(o) + heme-a(3)(r), was not observed with the A-type enzymes in our experiments but was observed with the Thermus ba(3); its Marcus parameters are λ = 1.5 eV, H(ab) = 26.6 × 10(-5) eV (2.14 cm(-1)), and βD = 9.35, consistent also with diabatic electron tunneling between the two hemes. The II-Glu15Ala mutation of the K-channel structure, ∼24 {\AA} between its CA and Fe-a(3), was found to completely block heme-b(r) to heme-a(3)(o) electron transfer. A structural mechanism is suggested to explain these observations.",

author = "Ole Farver and Scot Wherland and Antholine, {William E} and Gemmen, {Gregory J} and Ying Chen and Israel Pecht and Fee, {James A}",

year = "2022",

month = nov,

day = "15",

doi = "10.1021/bi100548n",

language = "English",

journal = "Biochemistry",

issn = "0006-2960",

publisher = "American Chemical Society",

}

TY - JOUR

T1 - Pulse Radiolysis Studies of Temperature Dependent Electron Transfers among Redox Centers in ba(3)-Cytochrome c Oxidase from Thermus thermophilus

T2 - Comparison of A- and B-Type Enzymes

AU - Farver, Ole

AU - Wherland, Scot

AU - Antholine, William E

AU - Gemmen, Gregory J

AU - Chen, Ying

AU - Pecht, Israel

AU - Fee, James A

PY - 2022/11/15

Y1 - 2022/11/15

N2 - The functioning of cytochrome c oxidases involves orchestration of long-range electron transfer (ET) events among the four redox active metal centers. We report the temperature dependence of electron transfer from the Cu(A)(r) site to the low-spin heme-(a)b(o) site, i.e., Cu(A)(r) + heme-a(b)(o) → Cu(A)(o) + heme-a(b)(r) in three structurally characterized enzymes: A-type aa(3) from Paracoccus denitrificans (PDB code 3HB3 ) and bovine heart tissue (PDB code 2ZXW ), and the B-type ba(3) from T. thermophilus (PDB codes 1EHK and 1XME ). k,T data sets were obtained with the use of pulse radiolysis as described previously. Semiclassical Marcus theory revealed that λ varies from 0.74 to 1.1 eV, H(ab), varies from ∼2 × 10(-5) eV (0.16 cm(-1)) to ∼24 × 10(-5) eV (1.9 cm(-1)), and βD varies from 9.3 to 13.9. These parameters are consistent with diabatic electron tunneling. The II-Asp111Asn Cu(A) mutation in cytochrome ba(3) had no effect on the rate of this reaction whereas the II-Met160Leu Cu(A)-mutation was slower by an amount corresponding to a decreased driving force of ∼0.06 eV. The structures support the presence of a common, electron-conducting "wire" between Cu(A) and heme-a(b). The transfer of an electron from the low-spin heme to the high-spin heme, i.e., heme-a(b)(r) + heme-a(3)(o) → heme-a(b)(o) + heme-a(3)(r), was not observed with the A-type enzymes in our experiments but was observed with the Thermus ba(3); its Marcus parameters are λ = 1.5 eV, H(ab) = 26.6 × 10(-5) eV (2.14 cm(-1)), and βD = 9.35, consistent also with diabatic electron tunneling between the two hemes. The II-Glu15Ala mutation of the K-channel structure, ∼24 Å between its CA and Fe-a(3), was found to completely block heme-b(r) to heme-a(3)(o) electron transfer. A structural mechanism is suggested to explain these observations.

AB - The functioning of cytochrome c oxidases involves orchestration of long-range electron transfer (ET) events among the four redox active metal centers. We report the temperature dependence of electron transfer from the Cu(A)(r) site to the low-spin heme-(a)b(o) site, i.e., Cu(A)(r) + heme-a(b)(o) → Cu(A)(o) + heme-a(b)(r) in three structurally characterized enzymes: A-type aa(3) from Paracoccus denitrificans (PDB code 3HB3 ) and bovine heart tissue (PDB code 2ZXW ), and the B-type ba(3) from T. thermophilus (PDB codes 1EHK and 1XME ). k,T data sets were obtained with the use of pulse radiolysis as described previously. Semiclassical Marcus theory revealed that λ varies from 0.74 to 1.1 eV, H(ab), varies from ∼2 × 10(-5) eV (0.16 cm(-1)) to ∼24 × 10(-5) eV (1.9 cm(-1)), and βD varies from 9.3 to 13.9. These parameters are consistent with diabatic electron tunneling. The II-Asp111Asn Cu(A) mutation in cytochrome ba(3) had no effect on the rate of this reaction whereas the II-Met160Leu Cu(A)-mutation was slower by an amount corresponding to a decreased driving force of ∼0.06 eV. The structures support the presence of a common, electron-conducting "wire" between Cu(A) and heme-a(b). The transfer of an electron from the low-spin heme to the high-spin heme, i.e., heme-a(b)(r) + heme-a(3)(o) → heme-a(b)(o) + heme-a(3)(r), was not observed with the A-type enzymes in our experiments but was observed with the Thermus ba(3); its Marcus parameters are λ = 1.5 eV, H(ab) = 26.6 × 10(-5) eV (2.14 cm(-1)), and βD = 9.35, consistent also with diabatic electron tunneling between the two hemes. The II-Glu15Ala mutation of the K-channel structure, ∼24 Å between its CA and Fe-a(3), was found to completely block heme-b(r) to heme-a(3)(o) electron transfer. A structural mechanism is suggested to explain these observations.

U2 - 10.1021/bi100548n

DO - 10.1021/bi100548n

M3 - Journal article

C2 - 21028883

SN - 0006-2960

JO - Biochemistry

JF - Biochemistry

ER -

Pulse Radiolysis Studies of Temperature Dependent Electron Transfers among Redox Centers in ba(3)-Cytochrome c Oxidase from Thermus thermophilus: Comparison of A- and B-Type Enzymes

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