Electrostatic interactions between charged amino acid residues and the bacteriochlorophyll dimer in reaction centers from rhodobacter sphaeroides

J. C. Williams, A. L M Haffa, J. L. McCulley, N. W. Woodbury, James Paul Allen

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

The extent of electrostatic contributions from the protein environment was assessed by the introduction of ionizable residues near the bacteriochlorophyll dimer in reaction centers from Rhodobacter sphaeroides. Two mutations at symmetry-related sites, M199 Asn to Asp and L170 Asn to Asp, resulted in a 48 and 44 mV lowering of the midpoint potential, respectively, compared to the wild type at pH 8, while a 75 mV decrease in the midpoint potential was observed for the mutation L168 His to Glu. The decrease relative to wild type was found to be approximately additive, up to 147 mV, for various combinations of the mutations. As the pH was lowered from 9.5 to 6.0, the relative decrease in the midpoint potential became smaller for each of these three mutations. Titration of the pH dependence of the change in midpoint potential of the M199 Asn to Asp mutant compared to wild type yielded a pKa value of 7.9 and a change in midpoint potential from low to high pH of 59 mV. The major effect of the mutation on the midpoint potential of the dimer is interpreted as stemming from a negative charge on the residue. An average dielectric constant of approximately 20 was estimated for the local protein environment, consistent with a relatively hydrophobic environment for residue M199. The rate of charge recombination between the primary quinone acceptor and the bacteriochlorophyll dimer decreased in the M199 Asn to Asp mutant at high pH, reflecting the decrease in midpoint potential.

Original languageEnglish
Pages (from-to)15403-15407
Number of pages5
JournalBiochemistry
Volume40
Issue number50
DOIs
Publication statusPublished - Dec 18 2001

Fingerprint

Bacteriochlorophylls
Rhodobacter sphaeroides
Coulomb interactions
Static Electricity
Dimers
Amino Acids
Viperidae
Mutation
Titration
Electrostatics
Proteins
Permittivity
Genetic Recombination

ASJC Scopus subject areas

  • Biochemistry

Cite this

Electrostatic interactions between charged amino acid residues and the bacteriochlorophyll dimer in reaction centers from rhodobacter sphaeroides. / Williams, J. C.; Haffa, A. L M; McCulley, J. L.; Woodbury, N. W.; Allen, James Paul.

In: Biochemistry, Vol. 40, No. 50, 18.12.2001, p. 15403-15407.

Research output: Contribution to journalArticle

Williams, J. C. ; Haffa, A. L M ; McCulley, J. L. ; Woodbury, N. W. ; Allen, James Paul. / Electrostatic interactions between charged amino acid residues and the bacteriochlorophyll dimer in reaction centers from rhodobacter sphaeroides. In: Biochemistry. 2001 ; Vol. 40, No. 50. pp. 15403-15407.
@article{beeced28bad14c169a63af14249f01be,
title = "Electrostatic interactions between charged amino acid residues and the bacteriochlorophyll dimer in reaction centers from rhodobacter sphaeroides",
abstract = "The extent of electrostatic contributions from the protein environment was assessed by the introduction of ionizable residues near the bacteriochlorophyll dimer in reaction centers from Rhodobacter sphaeroides. Two mutations at symmetry-related sites, M199 Asn to Asp and L170 Asn to Asp, resulted in a 48 and 44 mV lowering of the midpoint potential, respectively, compared to the wild type at pH 8, while a 75 mV decrease in the midpoint potential was observed for the mutation L168 His to Glu. The decrease relative to wild type was found to be approximately additive, up to 147 mV, for various combinations of the mutations. As the pH was lowered from 9.5 to 6.0, the relative decrease in the midpoint potential became smaller for each of these three mutations. Titration of the pH dependence of the change in midpoint potential of the M199 Asn to Asp mutant compared to wild type yielded a pKa value of 7.9 and a change in midpoint potential from low to high pH of 59 mV. The major effect of the mutation on the midpoint potential of the dimer is interpreted as stemming from a negative charge on the residue. An average dielectric constant of approximately 20 was estimated for the local protein environment, consistent with a relatively hydrophobic environment for residue M199. The rate of charge recombination between the primary quinone acceptor and the bacteriochlorophyll dimer decreased in the M199 Asn to Asp mutant at high pH, reflecting the decrease in midpoint potential.",
author = "Williams, {J. C.} and Haffa, {A. L M} and McCulley, {J. L.} and Woodbury, {N. W.} and Allen, {James Paul}",
year = "2001",
month = "12",
day = "18",
doi = "10.1021/bi011574z",
language = "English",
volume = "40",
pages = "15403--15407",
journal = "Biochemistry",
issn = "0006-2960",
publisher = "American Chemical Society",
number = "50",

}

TY - JOUR

T1 - Electrostatic interactions between charged amino acid residues and the bacteriochlorophyll dimer in reaction centers from rhodobacter sphaeroides

AU - Williams, J. C.

AU - Haffa, A. L M

AU - McCulley, J. L.

AU - Woodbury, N. W.

AU - Allen, James Paul

PY - 2001/12/18

Y1 - 2001/12/18

N2 - The extent of electrostatic contributions from the protein environment was assessed by the introduction of ionizable residues near the bacteriochlorophyll dimer in reaction centers from Rhodobacter sphaeroides. Two mutations at symmetry-related sites, M199 Asn to Asp and L170 Asn to Asp, resulted in a 48 and 44 mV lowering of the midpoint potential, respectively, compared to the wild type at pH 8, while a 75 mV decrease in the midpoint potential was observed for the mutation L168 His to Glu. The decrease relative to wild type was found to be approximately additive, up to 147 mV, for various combinations of the mutations. As the pH was lowered from 9.5 to 6.0, the relative decrease in the midpoint potential became smaller for each of these three mutations. Titration of the pH dependence of the change in midpoint potential of the M199 Asn to Asp mutant compared to wild type yielded a pKa value of 7.9 and a change in midpoint potential from low to high pH of 59 mV. The major effect of the mutation on the midpoint potential of the dimer is interpreted as stemming from a negative charge on the residue. An average dielectric constant of approximately 20 was estimated for the local protein environment, consistent with a relatively hydrophobic environment for residue M199. The rate of charge recombination between the primary quinone acceptor and the bacteriochlorophyll dimer decreased in the M199 Asn to Asp mutant at high pH, reflecting the decrease in midpoint potential.

AB - The extent of electrostatic contributions from the protein environment was assessed by the introduction of ionizable residues near the bacteriochlorophyll dimer in reaction centers from Rhodobacter sphaeroides. Two mutations at symmetry-related sites, M199 Asn to Asp and L170 Asn to Asp, resulted in a 48 and 44 mV lowering of the midpoint potential, respectively, compared to the wild type at pH 8, while a 75 mV decrease in the midpoint potential was observed for the mutation L168 His to Glu. The decrease relative to wild type was found to be approximately additive, up to 147 mV, for various combinations of the mutations. As the pH was lowered from 9.5 to 6.0, the relative decrease in the midpoint potential became smaller for each of these three mutations. Titration of the pH dependence of the change in midpoint potential of the M199 Asn to Asp mutant compared to wild type yielded a pKa value of 7.9 and a change in midpoint potential from low to high pH of 59 mV. The major effect of the mutation on the midpoint potential of the dimer is interpreted as stemming from a negative charge on the residue. An average dielectric constant of approximately 20 was estimated for the local protein environment, consistent with a relatively hydrophobic environment for residue M199. The rate of charge recombination between the primary quinone acceptor and the bacteriochlorophyll dimer decreased in the M199 Asn to Asp mutant at high pH, reflecting the decrease in midpoint potential.

UR - http://www.scopus.com/inward/record.url?scp=0035909814&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0035909814&partnerID=8YFLogxK

U2 - 10.1021/bi011574z

DO - 10.1021/bi011574z

M3 - Article

VL - 40

SP - 15403

EP - 15407

JO - Biochemistry

JF - Biochemistry

SN - 0006-2960

IS - 50

ER -