Isolation of Sperm Whale Myoglobin by Low Temperature Fractionation with Ethanol and Metallic Ions

Plant based production of myoglobin - a novel source of the muscle heme-protein

Myoglobin is a heme-protein in the muscle of vertebrates with important functions in the oxygenation of tissues and as a regulator in nitric oxide signaling. Myoglobin from many species is also an important nutritional source of bioavailable iron. In this study, we have successfully produced human myoglobin in the leaves of Nicotiana benthamiana by transient expression using a viral vector delivered by Agrobacterium tumefaciens. Analyses confirmed that heme was incorporated and the protein was functional, with observed properties consistent with those of native myoglobins. A relatively high degree of purity could be achieved with low cost methods. The results show the high potential of plants as a production platform for heme proteins, a group of proteins of interest for iron nutrition applications and possible future pharmaceutical development.

Synthetic Fe/Cu Complexes: Toward Understanding Heme-Copper Oxidase Structure and Function

Heme-copper oxidases (HCOs) are terminal enzymes on the mitochondrial or bacterial respiratory electron transport chain, which utilize a unique heterobinuclear active site to catalyze the 4H+/4e- reduction of dioxygen to water. This process involves a proton-coupled electron transfer (PCET) from a tyrosine (phenolic) residue and additional redox events coupled to transmembrane proton pumping and ATP synthesis. Given that HCOs are large, complex, membrane-bound enzymes, bioinspired synthetic model chemistry is a promising approach to better understand heme-Cu-mediated dioxygen reduction, including the details of proton and electron movements. This review encompasses important aspects of heme-O2 and copper-O2 (bio)chemistries as they relate to the design and interpretation of small molecule model systems and provides perspectives from fundamental coordination chemistry, which can be applied to the understanding of HCO activity. We focus on recent advancements from studies of heme-Cu models, evaluating experimental and computational results, which highlight important fundamental structure-function relationships. Finally, we provide an outlook for future potential contributions from synthetic inorganic chemistry and discuss their implications with relevance to biological O2-reduction.

Modeling heme protein active sites with the his93gly cavity mutant of sperm whale myoglobin: complexes with nitrogen-, oxygen- and sulfur-donor proximal ligands

Recent investigations of the His93Gly (H93G) "cavity" mutant of myoglobin as a versatile scaffold for modeling heme states are described. The difference in accessibility of the two sides of the heme in H93G myoglobin makes it possible to generate mixed ligand adducts in the ferric state that are difficult to prepare with heme models in organic solvents. In addition, the protection provided to the heme by the protein environment allows for the preparation of stable oxyferrous and oxo-iron(IV) complexes at near-ambient temperatures with variable ligands trans to the normally reactive dioxygen and oxo substituents. The extensive range of possible complexes that can be generated using the H93G system is illustrated with examples involving imidazole, phenolate, benzoate, thiolate and thiol ligands bound to the proximal side of the heme iron.

Myoglobin-H2O2 catalyzes the oxidation of β-ketoacids to α-dicarbonyls: mechanism and implications in ketosis

Acetoacetate (AA) and 2-methylacetoacetate (MAA) are accumulated in metabolic disorders such as diabetes and isoleucinemia. Here we examine the mechanism of AA and MAA aerobic oxidation initiated by myoglobin (Mb)/H(2)O(2). We propose a chemiluminescent route involving a dioxetanone intermediate whose thermolysis yields triplet α-dicarbonyl species (methylglyoxal and diacetyl). The observed ultraweak chemiluminescence increased linearly on raising the concentration of either Mb (10-500 μM) or AA (10-100 mM). Oxygen uptake studies revealed that MAA is almost a 100-fold more reactive than AA. EPR spin-trapping studies with MNP/MAA revealed the intermediacy of an α-carbon-centered radical and acetyl radical. The latter radical, probably derived from triplet diacetyl, is totally suppressed by sorbate, a well-known quencher of triplet carbonyls. Furthermore, an EPR signal assignable to MNP-AA(•) adduct was observed and confirmed by isotope effects. Oxygen consumption and α-dicarbonyl yield were shown to be dependent on AA or MAA concentrations (1-50 mM) and on H(2)O(2) or tert-butOOH added to the Mb-containing reaction mixtures. That ferrylMb is involved in a peroxidase cycle acting on the substrates is suggested by the reaction pH profiles and immunospin-trapping experiments. The generation of radicals and triplet dicarbonyl products by Mb/H(2)O(2)/β-ketoacids may contribute to the adverse health effects of ketogenic unbalance.

Challenges for the effective molecular imprinting of proteins

Molecular imprinting is a technique that is used to create artificial receptors by the formation of a polymer network around a template molecule. This technique has proven to be particularly effective for molecules with low molecular weight (<1500 Da), and during the past five years the number of research articles on the imprinting of larger (bio)templates is increasing considerably. However, expanding the methodology toward imprinted materials for selective recognition of proteins, DNA, viruses and bacteria appears to be extremely challenging. This paper presents a critical analysis of data presented by several authors and our own experiments, showing that the molecular imprinting of proteins still faces some fundamental challenges. The main topics of concern are proper monomer selection, washing method/template removal, quantification of the rebinding and reproducibility. Use of charged monomers can lead to strong electrostatic interactions between monomers and template but also to undesired high aspecific binding. Up till now, it has not been convincingly shown that electrostatic interactions lead to better imprinting results. The combination of a detergent (SDS) and AcOH, commonly used for template removal, can lead to experimental artifacts, and should ideally be avoided. In many cases template rebinding is unreliably quantified, results are not evaluated critically and lack statistical analysis. Therefore, it can be argued that presently, in numerous publications the scientific evidence of molecular imprinting of proteins is not convincing.

cDNA-derived amino acid sequences of myoglobins from nine species of whales and dolphins

We determined the myoglobin (Mb) cDNA sequences of nine cetaceans, of which six are the first reports of Mb sequences: sei whale (Balaenoptera borealis), Bryde's whale (Balaenoptera edeni), pygmy sperm whale (Kogia breviceps), Stejneger's beaked whale (Mesoplodon stejnegeri), Longman's beaked whale (Indopacetus pacificus), and melon-headed whale (Peponocephala electra), and three confirm the previously determined chemical amino acid sequences: sperm whale (Physeter macrocephalus), common minke whale (Balaenoptera acutorostrata) and pantropical spotted dolphin (Stenella attenuata). We found two types of Mb in the skeletal muscle of pantropical spotted dolphin: Mb I with the same amino acid sequence as that deposited in the protein database, and Mb II, which differs at two amino acid residues compared with Mb I. Using an alignment of the amino acid or cDNA sequences of cetacean Mb, we constructed a phylogenetic tree by the NJ method. Clustering of cetacean Mb amino acid and cDNA sequences essentially follows the classical taxonomy of cetaceans, suggesting that Mb sequence data is valid for classification of cetaceans at least to the family level.

Thermoglobin, Oxygen-avid Hemoglobin in a Bacterial Hyperthermophile

The hemoglobin family of proteins, ubiquitous in all domains of life, evolved from an ancestral protein of primordial function to extant hemoglobins that perform a myriad of functions with diverged biochemical properties. Study of homologs in bacterial hyperthermophiles may shed light on both mechanisms of adaptation to extreme conditions and the nature of the ancestral protein. A hemoglobin was identified in Aquifex aeolicus, cloned, recombinantly expressed, purified, and characterized. This hemoglobin is monomeric, resistant to thermal and chemical denaturation, pentacoordinate in the ferrous deoxygenated state, and oxygen-avid. The oxygen equilibrium dissociation constant is approximately 1 nm at room temperature, due in part to a hydrogen bond between the bound ligand and a tyrosine residue in the distal pocket. These biochemical properties of A. aeolicus thermoglobin, AaTgb, may have been shared by the ancestral hemoglobin, thus suggesting possible primordial functions and providing a starting point for consequent evolution of the hemoglobin family.

Fluorescence decay kinetics of the tryptophyl residues of myoglobin: effect of heme ligation and evidence for discrete lifetime components

The fluorescence decay kinetics of the tryptophyl residues of sperm whale and yellowfin tuna myoglobin have been determined by using time-correlated single photon counting, with picosecond resolution. Purification by HPLC techniques resulted in the isolation of samples that exclusively displayed picosecond decay kinetics. Lifetimes of 24.4 ps for Trp14 and 122.0 ps for Trp7 were found for oxy sperm whale myoglobin (pH 7), which agree with theoretical predictions [Hochstrasser, R. M., & Negus, D. K. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 4399-4403]. The effects of ligand binding and pH on the decay kinetics were investigated, and the results were shown to be consistent with the known crystal structures. Data for the met form of sperm whale myoglobin were analyzed both in terms of a sum of discrete exponential components and as a continuous gamma distribution of exponential decays. The results were not found to support the existence of multiple, structurally distinct conformation states in myoglobin.

Coordination geometry of heme in lactoperoxidase: pH-dependent 1H relaxivity and optical spectral studies

Molar relaxivity of water proton in lactoperoxidase solution was studied as a function of pH in the range of 2-13 by spin-lattice relaxation time measurements on a Bruker AM 500 MHz nuclear magnetic resonance (NMR) spectrometer. It was shown by comparison with the molar relaxivities of met myoglobin (Mb) and horseradish peroxidase (HRP) solutions that the sixth coordination position of the heme pocket in lactoperoxidase (LPO) is vacant. Distance of the water proton in the heme pocket from ferric ion was deduced to be 2.7, 3.6 and 4.3 A for Mb, HRP, and LPO, respectively. Acid-alkaline transition for met myoglobin, horseradish peroxidase, and lactoperoxidase determined from the pH dependence of changes in the Soret absorptions were found to be characterized by pK of 8.8, 10.9, and 12.1, respectively. Proton NMR of LPO at pH = 12.2 was found to have single broad resonance considerably upfield shifted as compared to that of LPO at neutral pH. By comparison with the proton NMR of HRP and Mb at pH greater than their respective pK of acid-alkaline transition, the upfield shifted proton resonance of LPO at pH = 12.2 was assigned to be due to low-spin LPO.

Kinetics of the reaction of compound II of horseradish peroxidase with hydrogen peroxide to form compound III

The kinetics of the reaction of H2O2 with compound II of horseradish peroxidase were studied as a function of pH at 25 degrees C and constant ionic strength of 0.11 M. The reaction of H2O2 with compound II involves the transient formation of ferric peroxidase and superoxide anion as the first step followed by the reaction of the intermediate species with H2O2 to form compound III. Both reactions are also observed with peracetic acid as substrate, though the amplitude of the first step was too small for the rate to be measured. Observation of the first reaction was not possible below pH 8.5 under the conditions of this investigation. It tends to occur faster at lower pH so an increasing fraction is lost in the dead time of the stopped-flow apparatus. The rate constants for the second reaction, leading to compound III formation, are small at all pH values, with a maximum of 20 M-1 s-1 at pH 7.0. Groups on the enzyme intermediate species with pKa values of 4.2 and 9.1 appear to be involved in this reaction. Compound III formation is accompanied by oxidation of aromatic amino acid groups on the protein. The compound III formed from horseradish peroxidase compound II and hydrogen peroxide has bands with molar absorption coefficients in excellent agreement with those obtained by flash photolysis of aerated carbonmonoxyperoxidase [Wittenberg, J. B., Noble, R. W., Wittenberg, B. A., Antonini, E., Brunori, M. and Wyman, J. (1967) J. Biol. Chem. 242, 626-634]. Attempts to use m-chloroperbenzoic acid as oxidant resulted in the destruction of compound II.

Reconstitution of myoglobin from apoprotein and heme, monitored by stopped-flow absorption, fluorescence and circular dichroism

The reconstitution reaction of ferric cyanomyoglobin from apomyoglobin and hemin dicyanide was investigated with a stopped-flow apparatus by the use of five kinds of probes; (a) Soret absorption, (b) fluorescence quenching of tryptophan, (c) far-ultraviolet CD, (d) near-ultraviolet CD, and (e) Soret CD. After mixing of apomyoglobulin with equimolar amounts of hemin dicyanide, the Soret absorption band was shifted to longer wavelengths within 10 ms. The shifted band kept its shape for a few seconds, and then gradually shifted to shorter wavelengths. A rate constant of the slow reaction was 1.1 x 10(-2) s-1. Time courses of fluorescence quenching followed a second-order reaction with a rate constant of 9 x 10(7) M-1 s-1. Far-ultraviolet CD recovered to the level of native state within the response time of an apparatus (= 64 ms). Near-ultraviolet CD and Soret CD changed with first-order rate constants of 5-30 s-1 and 5 x 10(-3) s-1 respectively. On the basis of the kinetic results we propose the following reconstitution pathway of myoglobin. Apomyoglobin has essentially a highly folded structure similar to myoglobin, but there are some differences in the secondary structure between them. In the first step, heme enters the pocket-like site of apomyoglobin and interacts with surrounding hydrophobic residues in the pocket, and then the interaction may give a complete ordered structure to the protein. Second, the tertiary structure of the heme pocket is partly constructed. Third, the iron-proximal His bond occurs, followed by the attainment of the final conformation. This sequence of the events shows that the polypeptide chain is entirely folded before the completion of three-dimensional structure of the heme pocket. The reconstitution pathway is fairly different from that of the alpha subunit of hemoglobin reported by Leutzinger and Beychok [Proc. Natl Acad. Sci. USA (1981) 78, 780-784], which described how a drastic recovery in helicity was observed on the heme-binding, and that the recovery is introduced by the formation of the heme pocket structure. The difference in the results found for the alpha subunit and myoglobin suggests a difference in conformation: in apomyoglobin most of the helices are arranged and folded around a helix core to form a compact structure as a whole, while in apo-alpha subunit some helices are not folded around the helix core. Helix D, which is absent in the alpha subunit, may play an important role in folding of the helices.

Morphometrics and ultrastructure of myocardial tissue in Notothenioid fishes

Antarctic fish of the family Channichthyidae (Icefishes) lack the respiratory pigments haemoglobin and myoglobin. The morphometrics and ultrastructure of the ventricular myocardium of a benthic icefish,Chaenocephalus aceratus has been compared with that of a red-blooded Notothenioid fish,Notothenia neglecta, of similar habit.The mass of ventricular muscle as a percentage of bodyweight is 3 times greater in adultC. aceratus (0.32%) thanN. neglecta (0.11%). Myoglobin concentration in the ventricle ofN. neglecta, 20 nmoles/g, is comparable to that of temperate teleosts with similar activity patterns. The volume and surface densities of mitochondria are 41.5% and 0.32 μm(-1) for Icefish and 25% and 0.15 μm(-1) forN. neglecta, Cytochrome oxidase activities are similar in the two tissues whilst the volume density of myofibrils is higher forN. neglecta (47%) thanC. aceratus (29.9%).The proliferation of mitochondria in the myocardium of Icefish will reduce the diffusion path-length for oxygen between ventricular lumen and the outer mitochondrial membrane and may compensate for the absence of myoglobin.

Direct formation of complexes between cytochrome P-450 and nitrosoarenes

The mechanism of the formation of the complexes between various nitrosobenzenes and cytochrome P-450 has been investigated. We have observed the formation of these complexes by a new and, as yet, undescribed route. Nitrosobenzene (NOB) itself reacts with cytochrome P-450 in the iron(III) state, in the absence of any exogenous reducing agent, to produce the iron(II)-NOB complex. Apparently, NOB is a ligand that is capable of causing the spontaneous autoreduction of the iron. The reduction of the iron may occur via ligand-induced oxidation of the axially bound thiolate of cytochrome P-450.

Oxygen binding to dithionite-reduced chloroperoxidase

Both the kinetics of ferric chloroperoxidase reduction by dithionite and the binding of molecular oxygen to ferrous chloroperoxidase have been studied. The oxyferrous chloroperoxidase decays spontaneously to the ferric enzyme. In addition the corresponding rapid-scan spectra have been recorded. The reduction reaction is caused by SO-.2 with a rate constant of (7.7 +/- 1.0) X 10(4) M-1 S-1. Oxygen binding occurs with a rate constant of (5.5 +/- 1.0) X 10(5) M-1 S-1 over the pH range 3.5-6. Oxyferrous chloroperoxidase has a Soret absorption peak at 428 nm and two partially resolved peaks at 555 nm and 588 nm. Isosbestic points occur at the following wavelengths: between ferrous and oxyferrous chloroperoxidase at 419, 545, 555 and 580 nm; between oxyferrous and ferric chloroperoxidase at 419, 487, 540, 609 and 682 nm.

Modification of the heme distal side in myoglobin by cyanogen bromide. Heme environmental structures and ligand binding properties of the modified myoglobin

Met, deoxy, and CO forms of myoglobin (Mb) react with a stoichiometric amount of cyanogen bromide (BrCN) to cause substantial changes in the 1H NMR, optical absorption, and infrared spectra. These spectral changes were interpreted as arising from the substantial alterations in the heme environments, most probably due to the modification of the histidine residue at the heme distal side. It is also revealed that the modified Mb does not combine with some exogenous ligands such as CN-, CH3NH2, and O2, although it does with N-3 or CO. These unique ligand binding properties are also discussed with relevance to a role of the distal histidine in stabilizing the coordinated ligand through a hydrogen bond and to a steric constraint.

Assignment of 1H NMR resonances of histidine and other aromatic residues in met-, cyano-, oxy-, and (carbon monoxy)myoglobins

The resolved 1H NMR resonances of the aromatic region in the 270-MHz NMR spectrum of sperm whale, horse, and pig metmyoglobin (metMb) have been assigned, including the observable H-2 and H-4 histidine resonances, the tryptophan H-2 resonances, and upfield-shifted resonances from one tyrosine residue. The use of different Mb species, carboxymethylation, and matching of pK values allows the assignment of the H-4 resonances, which agree in only three cases out of seven with scalar-correlated two-dimensional NMR spectroscopy assignments by others. The conversion to hydroxymyoglobin at high pH involves rearrangements throughout the molecule and is observed by many assigned residues. In sperm whale ferric cyanomyoglobin, nine H-2 and eight H-4 histidine resonances have been assigned, including the His-97 H-2 resonance and tyrosine resonances from residues 103 and 146. The hyperfine-shifted resonances from heme and near-heme protons observe a shift with a pK = 5.3 +/- 0.3 (probably due to deprotonation of His-97, pK = 5.6) and another shift at pK = 10.8 +/- 0.3. The spectrum of high-spin ferrous sperm whale deoxymyoglobin is very similar to that of metMb, which allows the assignment of seven surface histidine H-2 and H-4 resonances and also resonances from the two tryptophan residues and one tyrosine. In diamagnetic sperm whale (carbon monoxy)myoglobin (COMb), 10 His H-2 and 11 His H-4 resonances are observed, and 8 H-2 and 9 H-4 resonances are assigned, including His-64 H-4, the distal histidine. This important resonance is not observed in sperm whale oxymyoglobin, which in general shows very similar titration curves to COMb. Histidine-36 shows unusual titration behavior in the paramagnetic derivatives but normal behavior in the diamagnetic derivatives, which is discussed in the accompanying paper [Bradbury, J. H., & Carver, J. A. (1984) Biochemistry (following paper in this issue)].

Effects of ionizing radiation on nitric oxide myoglobin. Part 1. Effects on the NO-haem moiety

Bovine nitric oxide myoglobin (NOMb) was irradiated with 40-4000 krad of gamma-radiation, and the effects on the haem studied using absorption spectroscopy and electron spin resonance (e.s.r.) spectroscopy. The results show the following behaviour. The bright red colour of NOMb changes to brown upon irradiation. This is similar to changes observed in radiation sterilized. nitrite-containing meats. NOMb becomes progressively denitrosylated, with met-myoglobin (metMb) as the immediate product. Upon increasing doses of radiation (up to 800 krad) at 0 degrees C parallel to NOMb denitrosylation, metMb is gradually converted, by water radiolytic products, to other products, believed to be ferromyoglobin and ferrimyoglobin peroxide. A minor quantity of 'choleglobin-type' pigments may also be formed at the highest doses. Freezing of NOMb has a substantial protective effect against radiation. Native bovine NOMb behaves as a pentaco-ordinate (hfs of 3 peaks with equal intensity); the bond between iron and N epsilon is thus dramatically stretched and weakened. Using a thermal energy analyser, no NO could be detected over irradiated NOMb solution, indicating rapid reaction of NO liberated from NOMb by radiation, with radiolytic products of water.

Rapid micro-isolation of mammalian oxymyoglobin for biophysical studies

A rapid, single-step procedure is described for the isolation of mammalian oxymyoglobin for physical studies. The procedure employs a high-capacity, reusable, Hg-resin through which the myoglobin is filtered. The mammalian myoglobins for which sequences have been reported lack reactive cysteine. The column binds hemoglobin and other sulfhydryl-containing proteins, and retards other proteins. The procedure requires less than twenty minutes for the isolation of oxymyoglobin from homogenized muscle tissue. Virtually no metmyoglobin is formed. The yields are 2-3 times greater than by other methods. The procedure can easily be scaled down for isolation of myoglobin from a few milligrams of muscle. Identical rate constants for oxygen association, dissociation, and CO association were measured by laser photolysis for beef heart myoglobin prepared by this procedure and that of Yamazaki et al. (Yamazaki, I., Yokota, K. and Shikama, K. (1964) J. Biol. Chem. 239, 4151). Gel electrophoresis indicates that the preparation is at least 95% pure.