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H M Ranney

Publications and source records attributed to H M Ranney.

At least 37 records · Page 2Linked to original sources
PubMed1980

Kinetics of ligation reactions of rabbit hemoglobin in quaternary R and T states.

Rabbit hemoglobin shows significantly lower affinity for CO than does human hemoglobin (Hb A). The overall ligand combination and dissociation rate constants reveal, however, only small differences between Hb A rabbit Hb; this is mainly due to the fact that beta chains in rabbit hemoglobin determine the kinetics of ligand dissociation and combination. The heme environment in these chains is probably not very different in rabbit Hb and human Hb A. Rabbit hemoglobin alpha chains, on the other hand, exhibit greatly reduced CO and O2 combination rates in the R state and are primarily responsible for the overall low CO affinity of rabbit Hb. We postulate that the low ligand affinity of alpha chains in rabbit Hb is due to the substitution of larger residues at positions B10(Leu leads to Val), Cd6(Leu leads to Phe), and CD7(Ser leads to Thr). The possible implication of such substitutions for the kinetic and equilibrium properties of rabbit Hb are discussed.

Animals↗
PubMed1980

Bimane fluorescent labels. Characterization of the bimane labeling of human hemoglobin.

The products of the bimane labeling (using a monobromobimane, a dibromobimane and a quaternary bromobimane) of hemoglobin are characterized. Peptide mapping identifies cysteine-beta 93 as the reactive thiol site. Electrophoretic mobility of hemoglobin varies with the label used, that of monobromobimane-labeled hemoglobin being unaltered, while dibromobimane- and trimethylammoniobromobimane-labeled hemoglobin exhibit changes. The oxygen affinity of labeled hemoglobin is changed from that of hemoglobin. Deoxyhemoglobin is substantially less reactive towards monobromobimane than oxyhemoglobin. Bimane-labeled hemoglobin is more easily denatured on heating than unlabeled hemoglobin. Possible uses for bimane labels in the study of protein properties are pointed out. Bimane labeling agents are derivatives of 3,4,6,7-tetramethyl-1,5-diazabicyclo[3.3.0]-octa-3,6-diene-2,8-dione 9,10-dioxa-syn-(methyl,methyl)bimane).

Aza Compounds↗
PubMed1979

Bimane fluorescent labels: labeling of normal human red cells under physiological conditions.

The bimane fluorescent labels, monobromobimane, dibromobimane, and monobromotrimethylammoniobimane, are derivatives of syn-9,10-dioxabimane:1,5-diazabicyclo[3.3.0]octa-3,6-diene-2,8-dione. They efficiently label hemoglobin (reactive thiol groups), membrane proteins, and glutathione of normal human red cells under physiological conditions. Monobromobimane and dibromobimane are effective on intact cells while red cell membranes may be impermeable to the positively charged monobromotrimethylammoniobimane, the latter being effective only on lysed cells. These bimane labels provide a class of labeling agents that may have wide applicability in biological materials.

Aza Compounds↗
PubMed1978

The dissociation of NO from nitrosylhemoglobin.

The reaction between nitrosylhemoglobin and an excess of deoxymyoglobin has been used to study the kinetics of ligand dissociation from Hb4(NO)4 and Hb4(no)1 species. The kinetics of the dissociation of the first NO molecule from Hb4(no)4 was studied by the ligand replacement method. The results indicate that: (a) the ligand dissociation reaction in Hb4(NO)4 is a cooperative process. This is consistent with the results of Moore and Gibson (Moore, E.G., and Gibson, Q.H. (1977) J. Biol. Chem. 251, 2788-2794). (b) alpha and beta chains in the T state formed by adding IHP to Hb4(NO)4 show kinetic heterogeneity. (c) A similar kinetic heterogeneity is shown by alpha and beta chains in the species Hb4NO in the absence of IHP.(d) The value for the NO dissociation rate constant calculated from the slow phases observed in (b) and (c) is similar to that estimated for the R state. These results suggest that the R to T transition brought about with or without inositol hexaphosphate changes the ligand affinity of one type of the chains much more than of the other. On the basis of IR and EPR studies, it is suggested that alpha chains undergo larger functional changes in R to T transition (or vice versa) in nitrosylhemoglobin. The kinetic parameters for HbNO are compared with those of HbO2 and HbCO and the implications of the results for the reaction mechanism are discussed.

Carbon Monoxide↗
PubMed1978

"Tension" on heme by the proximal base and ligand reactivity: conclusions drawn from model compounds for the reaction of hemoglobin.

The kinetic data on model compounds of hemoglobin indicate that in oxyderivatives ligand dissociation rates are sensitive to the "tension" exerted by the proximal base on the metal-to-ligand bond; the corresponding rates for carboxy derivatives are not sensitive to the tension. It is suggested that the metal-to-ligand bond becomes weaker with increased "pull" (or tension) on Fe from the proximal base due to the steric and/or electronic interaction between the ligand, the porphyrin ring, and the proximal base. In model compounds the linear heme Fe-to-CO bound vis-a-vis the bent heme Fe-to-O2 bond probably makes such interactions less significant in carboxy derivatives. It is proposed that the kinetic alpha,beta-chain nonequivalence in Hb4(O2)4 is due to the difference in the tension in the two chains on Fe by the proximal base. The absence of alpha,beta-chain differences large enough to show up in CO dissociation rates from Hb4(CO)4 is explained on the basis of lack of sensitivity of the Fe-CO bound to tension from the proximal base. The implications of the results for the observed cooperative effects in ligand combination (for CO) and dissociation (for O2 and NO) rates of hemoglobin have also been discussed.

Carbon Monoxide↗
PubMed1978

Binding of 2,3-diphosphoglycerate by spectrin and its effect on oxygen affinity of hemoglobin.

The relationships between spectrin, a structural protein of the red blood cell (RBC) membrane facing the cytoplasm, and hemoglobin were studied. The oxygen-binding properties of stripped hemoglobin were not altered by the presence of spectrin, but the interaction of hemoglobin with organic phosphates was reduced by the addition of spectrin. The presence of the enzyme glyceraldehyde 3-phosphate dehydrogenase (G3PD), another component of the RBC membrane used as a control, did not change the oxygen affinity of either stripped hemoglobin or of hemoglobin solutions containing phosphates. Binding studies using the gel filtration method at pH 7.3 indicated reversible binding of 2,3-diphosphoglycerate to spectrin. A unit of 220,000 daltons was calculated to have seven binding sites and a binding constant of 1.2 X 10(4) M-1. A mechanism is proposed in which spectrin may facilitate oxygen transport for hemoglobin molecules reaching the membrane.

Binding, Competitive↗
PubMed1977

Interaction of hemoglobin with red blood cell membranes as shown by a fluorescent chromophore.

Hemoglobin quenching of the fluorescence intensity of 12-(9-anthroyl)stearic acid (AS) embedded in the red blood cell membrane occurs through an energy transfer mechanism and can be used to measure the binding of hemoglobin to the membrane. The binding of hemoglobin to red cell membranes was found to be reversible and electrostatic in nature. Using a theory of energy transfer based on Förster formulation, the quantitative data for the binding were derived. The number of binding sites was found to be 1.4 +/- 0.2 X 10(6) molecules per cell and the binding constant was 0.85 X 10(8) M-1.

Energy Transfer↗
PubMed1977

Classification and localization of hemoglobin binding sites on the red blood cell membrane.

The binding of hemoglobin to the red cell membrane was characterized over a wide range of free hemoglobin concentrations by measurement of membrane bound and supernatant hemoglobin. Scatchard analysis of the binding data revealed two classes of sites: high affinity sites with a binding constant of 1 X 10(8) M-1 and 1.2 X 10(6) sites per cell, and a second, low affinity class of sites with a binding constant of 6 X 10(6)M-1 and 6 X 10(6) sites per cell. The low affinity sites are shown to be nonspecific and appear to be a result of the ghost preparation. The high affinity sites are shown to be specific to the inner surface of the red cell membrane. The competition of hemoglobin and glyceraldehyde-3-phosphate dehydrogenase suggests band III proteins as a potential binding site for hemoglobin.

Binding Sites↗
PubMed1977

Hemoglobinopathies.

The determination of the structure of hemoglobin is one of the milestones of molecular biology. This information has provided an intimate understanding of the way in which the molecule functions physiologically; Study of hemoglobin has proved relevant to a number of biomedical disciplines. This protein is a prototype of a general class of allosteric enzymes whose function depends upon transition from one conformation to another. Recently, attention has been focused on environmental factors, including 2,3-DPG, hydrogen ion concentration, and CO2, which can modify and perhaps regulate the behavior of hemoglobin within the red cell. Comparisons of primary amino acid sequences of animal hemoglobins have provided new and independent phylogenetic insights. Furthermore, surveys of human hemoglobin phenotypes have been of considerable utility in the study of population genetics. Finally, certain variants are responsible for specific clinical syndromes. As we shall discuss in detail, in most cases the clinical features can be directly attributed to lesions at a submolecular level. This chapter will first present a detailed account of interrelationships between hemoglobin structure and function. Secondly, we will consider the various factors in health and disease which can modify hemoglobin's physiologic role. This background information will be useful in the consideration of inherited and acquired disorders of hemoglobin structure and function.

Anemia, Hemolytic, Congenital↗
PubMed1976

Dissociation of CO from carboxyhemoglobin.

The reaction between carboxyhemoglobin and reduced microperoxidase (MP): Hb4(CO)4 + 4MP=Hb4 + 4MPCO, recently reported by us, has been further studied. By generating species Hb4(CO), Hb4(CO)2, and Hb(CO)3 in the stopped flow cuvette by the reaction of dithionite with the species of the general formula Hb4(O2)x(CO)y(x + y=4) in the presence of microperoxidase it has been possible to determine the stepwise CO dissociation rate constants l4, l3, l2, and l1. The overall CO dissociation rate constant l, which is the same in this system as l4, is not affected by 2,3-diphosphoglyceric acid. The activation energy of the reaction is 21,400 cal in 15-25 degrees range. The ratio deltal/deltapH is approximately 3 in 6.5 to 7.5 pH range. The kinetic data indicate that, compared to HbO2, the contribution to the cooperativity of the dissociation rate constants of carboxyhemoglobin is greatly reduced. The ligand-dependent differences in the reactions of Hb with CO, O2, and NO suggest that in the combination reactions the ligand plays an active role in the rate-limiting step.

Carbon Monoxide↗
PubMed1976

Hemoglobin M equon beta 41 (C7) phenylalanine leads to tyrosine.

A severe hemolytic crisis was observed in a 34-yr-old female of English-Irish extraction following a viral illness treated with acetaminophen. Heinz bodies and heat instability were present only during a transient hemolytic event. A challenge dose of acetaminophen caused no detectable hematologic abnormality. Structural studies of the hemoglobin during hemolysis and again after complete recovery localized the abnormality to tryptic peptide beta Tp-5, and automated sequencing of I 125-labeled beta chains indicated a replacement of phenylalanine (C7) beta 41 by tyrosine. Substitution of the next residue, phenylalanine (CD1) beta 42 by serine (Hb Hammersmith), has resulted in chronic severe Heinz body hemolytic anemia. The lack of chronic anemia in the present disorder may reflect the different relationships of beta41 and beta 42 and/or the similarities in volume and hydrophobicity of tyrosine and phenylalanine. It is suggested that substitution of tyrosine for phenylalanine in Hb Mequon may disturb the critical environment around the heme group and render it susceptible to oxidative denaturation in the presence of infections and/or drugs.

Adult↗
PubMed1975

Hemoglobin components in diabetes mellitus: studies in identical twins.

The minor components of hemoglobin which are increased in subjects with diabetes mellitus, hemoglobin Ala-c, were measured in identical twins concordant and discordant for diabetes to determine whether the observed increases represent a genetically determined abnormality. The mean values for the proportion of hemoglobins Ala-c in discordant twins differed markedly in the two members of the pair: 10.4 +/- 0.74 per cent for the diabetic twins and 6.85 +/- 0.33 for the nondiabetic twins (t = 4.3811, P less than 0.005). In concordant twins with juvenile onset diabetes, the mean proportion of Hb Ala-c was 11.4 per cent, and no marked differences were observed between members of twin pairs. Four pairs of identical twins concordant for maturity onset diabetes showed lower mean values for Hb Ala-c but did not show marked intra-pair differences. Thus, the abnormal proportions of hemoglobins Ala-c found in the presence of overt diabetes mellitus appear to be a manifestation of a metabolic abnormality of diabetes.

Adolescent↗
PubMed1975

Rat haemoglobin heterogeneity. Two structurally distinct alpha chains and functional behaviour of selected components.

Six haemoglobins were separated analytically from haemolysates of adult Wistar rats (Rattus norvegicus) by cellulose acetate electrophoresis and preparatively by DEAE-cellulose chromatography. The globin chains were separated from unfractionated haemolysates by CM-cellulose chromatography by using a non-linear formic acid-pyridine gradient followed by CM-cellulose chromatography in 8M-urea by using a gradient of increasing Na+ concentration in phosphate buffer, pH 6.7. Two alpha chains and three non-alpha chains were identified. Chains isolated from purified haemoglobins were correlated with chains isolated from unfractionated haemolysates by electrophoresis on urea-starch gels to make presumptive assignments of the subunit composition of the six haemoglobin tetramers. Partial amino acid sequences were determined for the major and minor alpha chains. The oxygen equilibria of two of the major haemoglobin components and of the unfractionated haemolysate were examined at pH 7.5 and 8.0. The two purified haemoglobins exhibited similar oxygen affinities; the haemolysate, however, had a lower oxygen affinity than either of the two purified haemoglobins. Both the haemolysate and the two haemoglobins showed an alkaline Bohr effect larger than that of human haemoglobin A.

Amino Acid Sequence↗