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A Arnone

Publications and source records attributed to A Arnone.

At least 55 records · Page 3Linked to original sources
PubMed1984

Structural and functional studies of hemoglobin Wayne: an elongated alpha-chain variant.

Hemoglobin Wayne (Hb Wayne) is a frame-shift, elongated alpha-chain variant that exists in two forms, with either asparagine or aspartic acid as residue 139. Oxygen equilibrium studies showed that stripped Hb Wayne Asn and Hb Wayne Asp possessed high oxygen affinity (P 1/2 = 0.60 and 0.23 mmHg at pH 7, respectively), were non-co-operative and have a markedly reduced Bohr effect (-delta log P 1/2/pH (7 to 8) = 0.34 and 0.10, respectively). Adding organic phosphate results in a decreased oxygen affinity and increased Bohr effect for both Hbs Wayne. The overall rate of carbon monoxide binding at pH 7 (l' = 5.6 X 10(6) M-1 S-1) was similar for both stripped Hbs Wayne and was 25-fold more rapid than that of stripped Hb A. When organic phosphate was added, Hb Wayne Asn exhibited a homogeneous slower rate of carbon monoxide binding (l' = 2.6 X 10(6) M-1 S-1), whereas Hb Wayne Asp showed heterogeneous binding (l' = 6.1 X 10(6) and 2.6 X 10(6) M-1 S-1 for fast and slow phases, respectively). The rates of overall oxygen dissociation and oxygen dissociation with carbon monoxide replacement for both Hbs Wayne were found to be slow compared to Hb A and uniquely different from each other. Similarly, sedimentation velocity experiments indicated that, although Hb Wayne Asn and Hb Wayne Asp were both less tetrameric than Hb A, each hemoglobin exhibited a distinct degree of oxygen-linked subunit dissociation. These observed differences in the allosteric properties of Hb Wayne Asn and Hb Wayne Asp appeared to be directly attributable to residue 139. The equilibrium and kinetic data are consistent with the X-ray diffraction analysis of Hb Wayne Asp, which shows that the C terminus of the deoxytetramers are severely disordered, a condition that results in major destabilization of the T conformation and disruption of normal hemoglobin function.

Amino Acid Sequence↗
PubMed1984

The interaction of hemoglobin with the cytoplasmic domain of band 3 of the human erythrocyte membrane.

Previous studies point to the acidic amino-terminal segment of band 3, the anion transport protein of the red cell, as the common binding site for hemoglobin and several of the glycolytic enzymes to the erythrocyte membrane. We now report on the interaction of hemoglobin with the synthetic peptide AcM-E-E-L-Q-D-D-Y-E-D-E, corresponding to the first 11 residues of band 3, and with the entire 43,000-Da cytoplasmic domain of the protein. In the presence of increasing concentrations of the peptide, the oxygen binding curve for hemoglobin is shifted progressively to the right, indicating that the peptide binds preferentially to deoxyhemoglobin. The dissociation constant for the deoxyhemoglobin-peptide complex at pH 7.2 in the presence of 100 mM NaCl is 0.31 mM. X-ray crystallographic studies were carried out to determine the exact mode of binding of the peptide to deoxyhemoglobin. The difference electron density map of the deoxyhemoglobin-peptide complex at 5 A resolution showed that the binding site extends deep (approximately 18 A) into the central cavity between the beta chains, along the dyad symmetry axis, and includes Arg 104 beta 1 and Arg 104 beta 2 as well as most of the basic residues within the 2,3-diphosphoglycerate binding site. The peptide appears to have an extended conformation with only 5 to 7 of the 11 residues in contact with hemoglobin. In agreement with the crystallographic studies, binding of the peptide to deoxyhemoglobin was blocked by cross-linking the beta chains at the entrance to the central cavity. Oxygen equilibrium studies showed that the isolated cytoplasmic fragment of band 3 also binds preferentially to deoxyhemoglobin. The binding of the 43,000-Da fragment to hemoglobin was inhibited in the cross-linked derivative indicating that the acidic amino-terminal residues in the intact cytoplasmic domain also bind within the central cavity of the hemoglobin tetramer.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1982

Transaminases.

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Chemical Phenomena↗
PubMed1981

The structure of hemoglobin Creteil (beta 89 Ser replaced by Asn) is similar to that of abnormal human hemoglobins having sequence changes at Tyr 145 beta.

In normal deoxyhemoglobin A, the beta chain COOH-terminal peptide adopts a well ordered structure which is needed for the full expression of allosteric action. Our crystallographic studies of deoxyhemoglobin Creteil (beta 89 Ser replaced by Asn), a variant hemoglobin characterized by high oxygen affinity and a very low level of allosteric function, show that replacement of Ser 89 beta by asparagine causes severe disordering of the beta chain COOH-terminal tetrapeptide. This results, as shown by our spectroscopic studies, in the destabilization of the quaternary structure of deoxyhemoglobin Creteil. We find, furthermore, that the changes in tertiary structure observed in deoxyhemoglobin Creteil are common to other variant hemoglobins having similar functional abnormalities but very different changes in primary structure. In particular, direct comparison of the difference electron density map of deoxyhemoglobin Creteil with that of deoxyhemoglobin Nancy (beta 145 Tyr replaced by Asp) suggests that these two abnormal hemoglobins may have the same mechanism of dysfunction despite the very different nature of their respective sequence changes.

Amino Acid Sequence↗
PubMed1980

Structural and functional studies of hemoglobin Suresnes (arg 141 alpha 2 replaced by His beta 2). Consequences of disrupting an oxygen-linked anion-binding site.

Hb Suresnes is a human hemoglobin variant in which histidine replaces arginine at the COOH terminus of the alpha chains. The COOH-terminal arginines of the alpha chains play a major role in normal human hemoglobin (HbA), both by electrostatic interactions which constrain deoxygenated hemoglobin in a low affinity quaternary conformation and by involvement in oxygen-linked anion binding knoiwn to give rise to a large part of the alkaline Bohr effect. An x-ray crystallographic analysis of deoxyHb Suresnes reveals the loss of the normal intersubunit salt bridge to lysine 127 alpha and a decrease in the occupancy of inorganic anions at the alpha chain aniom-binding site. Relative to normal HbA, Hb Suresnes has a high affinity for oxygen, a reduced cooperativity in oxygen biding, and greatly reduced pH and chloride sensitivity. similar changes are found in carboxypeptidase B-digested hemoglobin Ao where the COOH-terminal arginine is removed by enzymatic digestion. Both equilibrium and kinetic manifestations of the destabilization of the normal low affinity configuration are observed. Inositol hexaphosphate restores cooperativity and pH sensitivity but, even in the presence of this strong allosteric effector, the low and high affinity conformations of Hb Suresnes appear to differ from those of HbA. In both the unliganded and liganded states, apreciable subunit dissociation of Hb Suresnes is apparent, which suggests that the substitution disrupts bonds which normally stabilize the tetramer. Structural changes at both the quaternary and tertiary level appear to contribute to alterations in the high and low affinity conformations of ths abnormal hemoglobin. Hb Suresnes thus illustrtaes the consequences of the loss of an important oxygen-linked anion-binding site.

Anions↗
PubMed1978

Crystalline enzyme.substrate complexes of asparate aminotransferase.

Crystalline complexes of cytoplasmic aspartate aminotransferase of pig heart with the substrates L-glutamate and L-aspartate, and with other amino acids, have been prepared and polarized light absorption spectra have been measured. Striking differences in the directions of polarization of the absorption bands are seen. A complete half-transamination of pyridoxal phosphate to pyridoxamine phosphate by aspartate or by cysteine sulfinate can be demonstrated in the crystal as can the accumulation of a quinonoid intermediate with erythro-beta-hydroxyaspartate. X-ray diffraction studies show that the crystals with erythro-beta-hydroxyaspartate and alpha-methylaspartate are isomorphous with those of both alpha and beta subforms of the native enzyme.

Amino Acids↗
PubMed1977

Specific modification of the alpha chain C-terminal carboxyl group of hemoglobin by trypsin-catalyzed hydrazinolysis.

In human deoxyhemoglobin a salt bridge links the alpha carboxyl of Arg-141 of each alpha chain to the epsilon-amino group of Lys-127 of the opposite alpha chain. These salt bridges are believed to contribute to the constraints in the quaternary deoxy (T) structure that lower its oxygen affinity. We have tested this hypothesis by incubating hemoglobin with 2 M hydrazine and trypsin which catalyzes specifically the reversible hydrazinolysis of the alpha carboxyl of Arg-141alpha. X-ray analysis shows the major structural difference between native deoxyhemoglobin and hydrazide deoxyhemoglobin to be the loss of the Arg-141alpha1-Lys-127alpha2 salt bridge and its Arg-141alpha2-Lys-127alpha1 counterpart. Accurate oxygen equilibrium curves of hydrazide hemoglobin show that blocking of the salt bridge has raised the oxygen affinity of the T structure while leaving that of the quaternary oxy (R) structure unchanged.

Amino Acid Sequence↗
PubMed1977

The binding of zinc to human deoxyhemoglobin and its possible relevance to the anti-sickling effect of zinc.

We find only one major zinc binding site in crystals of deoxyhemoglobin A. It is located at an interface between adjacent tetramers where residues histidine 116, histidine 117, and glutamate 26 on the beta 1 chain of one tetramer are in close proximity to lysine 16 and glutamate 116 on the alpha 2 chain of a neighboring tetramer. If this intertetramer contact does not exist in the rigid fibers of polymerized deoxyhemoglobin S, then low levels of zinc may promote its formation at random points along the fiber and thereby inhibit the formation of long fibers.

Anemia, Sickle Cell↗