Steric factors moderate conformational fluidity and contribute to the high proton sensitivity of Root effect hemoglobins

Celia Bonaventura, Robert Henkens, Joel M. Friedman, Claire J Parker Siburt, Daniel Kraiter, Alvin L. Crumbliss

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

The structural basis of the extreme pH dependence of oxygen binding to Root effect Hbs is a long-standing puzzle in the field of protein chemistry. A previously unappreciated role of steric factors in the Root effect was revealed by a comparison of pH effects on oxygenation and oxidation processes in human Hb relative to Spot (Leiostomus xanthurus) and Carp (Cyprinodon carpio) Hbs. The Root effect confers five-fold increased pH sensitivity to oxygenation of Spot and Carp Hbs relative to Hb A0 in the absence of anionic effectors, and even larger relative elevations of pH sensitivity of oxygenation in the presence of 0.2 M phosphate. Remarkably, the Root effect was not evident in the oxidation of the Root effect Hbs. This finding rules out pH-dependent alterations in the thermodynamic properties of the heme iron, measured in the anaerobic oxidation reaction, as the basis of the Root effect. The alternative explanation supported by these results is that the elevated pH sensitivity of oxygenation of Root effect Hbs is attributable to globin-dependent steric effects that alter oxygen affinity by constraining conformational fluidity, but which have little influence on electron exchange via the heme edge. This elegant mode of allosteric control can regulate oxygen affinity within a given quaternary state, in addition to modifying the T-R equilibrium. Evolution of Hb sequences that result in proton-linked steric barriers to heme oxygenation could provide a general mechanism to account for the appearance of the Root effect in the structurally diverse Hbs of many species.

Original languageEnglish (US)
Pages (from-to)1261-1268
Number of pages8
JournalBiochimica et Biophysica Acta - Proteins and Proteomics
Volume1814
Issue number10
DOIs
StatePublished - Oct 2011

Fingerprint

Oxygenation
Fluidity
Protons
Hemoglobins
Heme
Killifishes
Oxygen
Oxidation
pH effects
Globins
Thermodynamics
Thermodynamic properties
Iron
Phosphates
Electrons
Proteins

Keywords

  • Allostery
  • Conformational fluidity
  • Hemoglobin
  • Redox potential
  • Root effect
  • Steric controls

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Analytical Chemistry
  • Molecular Biology

Cite this

Steric factors moderate conformational fluidity and contribute to the high proton sensitivity of Root effect hemoglobins. / Bonaventura, Celia; Henkens, Robert; Friedman, Joel M.; Siburt, Claire J Parker; Kraiter, Daniel; Crumbliss, Alvin L.

In: Biochimica et Biophysica Acta - Proteins and Proteomics, Vol. 1814, No. 10, 10.2011, p. 1261-1268.

Research output: Contribution to journalArticle

Bonaventura, Celia ; Henkens, Robert ; Friedman, Joel M. ; Siburt, Claire J Parker ; Kraiter, Daniel ; Crumbliss, Alvin L. / Steric factors moderate conformational fluidity and contribute to the high proton sensitivity of Root effect hemoglobins. In: Biochimica et Biophysica Acta - Proteins and Proteomics. 2011 ; Vol. 1814, No. 10. pp. 1261-1268.
@article{41cca834fb0741189a3566aa0ce3e463,
title = "Steric factors moderate conformational fluidity and contribute to the high proton sensitivity of Root effect hemoglobins",
abstract = "The structural basis of the extreme pH dependence of oxygen binding to Root effect Hbs is a long-standing puzzle in the field of protein chemistry. A previously unappreciated role of steric factors in the Root effect was revealed by a comparison of pH effects on oxygenation and oxidation processes in human Hb relative to Spot (Leiostomus xanthurus) and Carp (Cyprinodon carpio) Hbs. The Root effect confers five-fold increased pH sensitivity to oxygenation of Spot and Carp Hbs relative to Hb A0 in the absence of anionic effectors, and even larger relative elevations of pH sensitivity of oxygenation in the presence of 0.2 M phosphate. Remarkably, the Root effect was not evident in the oxidation of the Root effect Hbs. This finding rules out pH-dependent alterations in the thermodynamic properties of the heme iron, measured in the anaerobic oxidation reaction, as the basis of the Root effect. The alternative explanation supported by these results is that the elevated pH sensitivity of oxygenation of Root effect Hbs is attributable to globin-dependent steric effects that alter oxygen affinity by constraining conformational fluidity, but which have little influence on electron exchange via the heme edge. This elegant mode of allosteric control can regulate oxygen affinity within a given quaternary state, in addition to modifying the T-R equilibrium. Evolution of Hb sequences that result in proton-linked steric barriers to heme oxygenation could provide a general mechanism to account for the appearance of the Root effect in the structurally diverse Hbs of many species.",
keywords = "Allostery, Conformational fluidity, Hemoglobin, Redox potential, Root effect, Steric controls",
author = "Celia Bonaventura and Robert Henkens and Friedman, {Joel M.} and Siburt, {Claire J Parker} and Daniel Kraiter and Crumbliss, {Alvin L.}",
year = "2011",
month = "10",
doi = "10.1016/j.bbapap.2011.06.012",
language = "English (US)",
volume = "1814",
pages = "1261--1268",
journal = "Biochimica et Biophysica Acta - Proteins and Proteomics",
issn = "1570-9639",
publisher = "Elsevier",
number = "10",

}

TY - JOUR

T1 - Steric factors moderate conformational fluidity and contribute to the high proton sensitivity of Root effect hemoglobins

AU - Bonaventura, Celia

AU - Henkens, Robert

AU - Friedman, Joel M.

AU - Siburt, Claire J Parker

AU - Kraiter, Daniel

AU - Crumbliss, Alvin L.

PY - 2011/10

Y1 - 2011/10

N2 - The structural basis of the extreme pH dependence of oxygen binding to Root effect Hbs is a long-standing puzzle in the field of protein chemistry. A previously unappreciated role of steric factors in the Root effect was revealed by a comparison of pH effects on oxygenation and oxidation processes in human Hb relative to Spot (Leiostomus xanthurus) and Carp (Cyprinodon carpio) Hbs. The Root effect confers five-fold increased pH sensitivity to oxygenation of Spot and Carp Hbs relative to Hb A0 in the absence of anionic effectors, and even larger relative elevations of pH sensitivity of oxygenation in the presence of 0.2 M phosphate. Remarkably, the Root effect was not evident in the oxidation of the Root effect Hbs. This finding rules out pH-dependent alterations in the thermodynamic properties of the heme iron, measured in the anaerobic oxidation reaction, as the basis of the Root effect. The alternative explanation supported by these results is that the elevated pH sensitivity of oxygenation of Root effect Hbs is attributable to globin-dependent steric effects that alter oxygen affinity by constraining conformational fluidity, but which have little influence on electron exchange via the heme edge. This elegant mode of allosteric control can regulate oxygen affinity within a given quaternary state, in addition to modifying the T-R equilibrium. Evolution of Hb sequences that result in proton-linked steric barriers to heme oxygenation could provide a general mechanism to account for the appearance of the Root effect in the structurally diverse Hbs of many species.

AB - The structural basis of the extreme pH dependence of oxygen binding to Root effect Hbs is a long-standing puzzle in the field of protein chemistry. A previously unappreciated role of steric factors in the Root effect was revealed by a comparison of pH effects on oxygenation and oxidation processes in human Hb relative to Spot (Leiostomus xanthurus) and Carp (Cyprinodon carpio) Hbs. The Root effect confers five-fold increased pH sensitivity to oxygenation of Spot and Carp Hbs relative to Hb A0 in the absence of anionic effectors, and even larger relative elevations of pH sensitivity of oxygenation in the presence of 0.2 M phosphate. Remarkably, the Root effect was not evident in the oxidation of the Root effect Hbs. This finding rules out pH-dependent alterations in the thermodynamic properties of the heme iron, measured in the anaerobic oxidation reaction, as the basis of the Root effect. The alternative explanation supported by these results is that the elevated pH sensitivity of oxygenation of Root effect Hbs is attributable to globin-dependent steric effects that alter oxygen affinity by constraining conformational fluidity, but which have little influence on electron exchange via the heme edge. This elegant mode of allosteric control can regulate oxygen affinity within a given quaternary state, in addition to modifying the T-R equilibrium. Evolution of Hb sequences that result in proton-linked steric barriers to heme oxygenation could provide a general mechanism to account for the appearance of the Root effect in the structurally diverse Hbs of many species.

KW - Allostery

KW - Conformational fluidity

KW - Hemoglobin

KW - Redox potential

KW - Root effect

KW - Steric controls

UR - http://www.scopus.com/inward/record.url?scp=79960556322&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=79960556322&partnerID=8YFLogxK

U2 - 10.1016/j.bbapap.2011.06.012

DO - 10.1016/j.bbapap.2011.06.012

M3 - Article

VL - 1814

SP - 1261

EP - 1268

JO - Biochimica et Biophysica Acta - Proteins and Proteomics

JF - Biochimica et Biophysica Acta - Proteins and Proteomics

SN - 1570-9639

IS - 10

ER -