The structure of horse methaemoglobin at 2.0 Å resolution

Ladner, Robert C.; Heidner, Elizabeth J.; Perutz, M. F.

doi:10.1016/0022-2836(77)90256-x

Cited by 289 publications

(121 citation statements)

References 32 publications

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“…found in the comparison of this structure with the earlier human carboxyhemoglobin (Baldwin & Chothia, 1979;Baldwin, 1980) and horse methemoglobin (Ladner et al, 1977) supported proposals for the allosteric mechanism that were based on models for oxyhemogiobin constructed from these early R-state structures (Perutz, 1970;Baldwin & Chothia, 1979).…”

supporting

confidence: 73%

“…Once the structure was oriented in the unit cell, map fitting and real-space refinement (Diamond, 1971(Diamond, , 1974 augmented by energy refinement (Levitt, 1974) were used to obtain the final coordinates. Baldwin & Chothia (1979) compared the R-state carboxyhemoglobin structure with that of the T-state deoxyhemoglobin determined at 2.5 ,~ resolution (Fermi, 1975) and another R-state structure, horse methemoglobin at 2.0,4, resolution (Ladner et al, 1977). Their extensive analysis established that the residues at the c~1/31 and c~2fl2 dimer interfaces maintain their conformations, and thus the subunits in the dimers maintain their relative positions to one another.…”

mentioning

confidence: 99%

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Human Carboxyhemoglobin at 2.2 Å Resolution: Structure and Solvent Comparisons of R-State, R2-State and T-State Hemoglobins

Vasquez

Fronticelli

et al. 1998

Acta Crystallogr D Biol Cryst

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supporting

confidence: 73%

mentioning

confidence: 99%

Human Carboxyhemoglobin at 2.2 Å Resolution: Structure and Solvent Comparisons of R-State, R2-State and T-State Hemoglobins

Vasquez

Fronticelli

et al. 1998

Acta Crystallogr D Biol Cryst

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“…The results of the ultrasonic titration curve indicate that the tertiary structure at the a-chain N-termini resembles that of oxyhemoglobin for both carbonmonoxyhemoglobin and aquomethemoglobin. This is in accordance with the finding that the a-chain N-termini of aquomethemoglobin and carbonmonoxyhemoglobin [16,20] give only a very weak signal on the electron density map, which suggests that they rotate freely.…”

Section: Resultssupporting

confidence: 92%

Ligand‐Linked Changes of Ultrasound Absorption of Hemoglobin

Jürgens

Baumann

Röbbel

1980

European Journal of Biochemistry

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The acoustic absorption of hemoglobin solutions at 1.88 MHz has been studied in dependence of ligand binding and pH. In the physiological pH range the excess absorption of oxyhemoglobin is increased compared to deoxyhemoglobin. Evidence is presented that in human hemoglobin the additional absorption of oxyhemoglobin is caused by a proton transfer relaxation process involving the a chain N-terminal a-amino groups. This process cannot be observed in deoxyhemoglobin because of fixation of the N-terminal a-amino groups in a salt bridge. Further investigations of carbonmonoxy, nitrosyl, aquomethemoglobin and fluoromethemoglobin in the absence and presence of inositol hexakissulfate show that acoustic absorption measurements offer an additional tool to characterize in greater detail the different conformational states of hemoglobin.The study of conformational changes in the globin part of the hemoglobin molecule, associated with ligand binding, is a central problem of hemoglobin chemistry. In recent years increasing use has been made of relaxation methods, which have significantly increased knowledge about the dynamical aspects of conformational equilibria. A major problem associated with the use of relaxation methods in protein chemistry is that the complexity of the protein structure very often makes it difficult to assign to an observed signal change a specific type of relaxation process or identify the specific groups involved. This is especially the case with ultrasound methods, where hemoglobin has served as a model protein for analysis of specific sound-absorbing processes in several studies. A satisfactory explanation for processes causing excess sound absorption in the MHz frequency range has been advanced only for the absorption maxima found in the very acidic (pH < 3.5) and alkaline (pH > 11) ranges. There the excess sound absorption seems to be caused predominantly by dissociative proton transfer reactions of the basic and acidic amino acid sidechains [I, 21. Processes responsible for sound absorption in the pH range between 6 and 9, i.e. the physiologically important pH range, are less well established. There are, however, several results pointing towards an important role of direct internal proton transfers between adjacent amino acid side-chains as contributors to excess sound absorption at neutral pH. Thus, White and Slutsky [3] have computed that in bovine hemoglobin one internal direct proton transfer Abbreviations. Hb, hemoglobin; Mb, myoglobin. per aP dimer could theoretically account for up to 25 % of the total acoustic excess absorption observed at neutral pH [3].With one exception ultrasound studies on hemoglobin have not been concerned with the question of whether a difference in ultrasound absorption exists between oxy and deoxyhemoglobin. The work of Schneider et al.[4] on bovine hemoglobin gave no conclusive evidence about significant differences in ultrasound absorption of oxy and deoxyhemoglobin. The present study investigates ligand-dependent changes in excess acoustic absorption of he...

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“…(1978) tates essentially as a rigid body by 120 relative to the rest of the molecule, causing movements of as much as 8 A in the polypeptide backbone. This conformational change is comparable in both nature and magnitude to the change in quaternary structure seen in the allosteric transition of hemoglobin, in which the two ag dimers rotate 14°relative to one another as rigid units (21,25). Intrasubunit flexibility involving entire domains has also been observed in tomato bushy stunt virus coat protein (26) and in immunoglobulins (27).…”

Section: Discussionmentioning

confidence: 66%