Mammalian cytochrome b

Digestion of a preparation of cytochromes b and c(1) with pancreatic protease followed by ammonium sulfate precipitation resulted in a soluble cytochrome b uncontaminated by cytochrome C(l). This preparation, which was free of succinic dehydrogenase and cytochrome oxidase activity, had an estimated deltaE(1 cm)(1g/ml) of 102 for its alpha-peak. In the reduced form absorption maxima were found at 560 to 562, 530 to 532, and 427 to 428 mmicro, and in the oxidized form, at 413 mmicro.     

CYTOCHROME FUNCTION IN RELATION TO INNER MEMBRANE STRUCTURE OF MITOCHONDRIA

Projecting subunits of an average diameter of 80 A are found on the cristae of mitochondria prepared from the muscle of Ascaris lumbricoides. A spectroscopic examination of the cytochrome content of these mitochondria shows no detectable cytochrome c(1), a, or a(3) and does reveal cytochromes of types c and b. Subunits in the same size range are found in cytochrome c deficient mitochondria of the emergent bee, while the frequency of their occurrence along the cristae is decreased relative to the adult bee. Apparently, the cytochrome content of the respiratory chain is not related to the size of the subunits, but may be related to the frequency of occurrence of the subunits.     

Antibodies to rabbit cytochrome c arising in rabbits

Antibodies reactive with rabbit cytochrome c have been observed in rabbits immunized with several heterologous cytochromes. Such antibodies have also been observed in rabbits immunized with rabbit cytochrome c conjugated to bovine gamma globulin. The serum of a rabbit immunized with human cyto chrome c reacted with the cytochrome c of the same rabbit.     

Monoclonal antibody-directed radioimmunoassay detects cytochrome P-450 in human placenta and lymphocytes

A multiplicity of cytochromes P-450 is responsible for the detoxification and activation of xenobiotics such as drugs and carcinogens. Individual differences in sensitivity to these agents may reside in the cytochrome P-450 phenotype. A monoclonal antibody-directed radioimmunoassay was developed that detects epitope-specific cytochromes P-450 in human placentas and peripheral lymphocytes. Placentas from women who smoked cigarettes contained greater amounts of cytochrome P-450 with the monoclonal antibody-specific epitope than placentas from nonsmokers. The amount of this cytochrome P-450 in human peripheral lymphocytes increased after treatment of the mitogenized lymphocytes with the cytochrome P-450 inducer benz[a]anthracene.     

Probing the mechanisms of macromolecular recognition: the cytochrome b5-cytochrome c complex

The specificity of complex formation between cytochrome b5 (cyt b5) and cytochrome c (cyt c) is believed to involve the formation of salt linkages between specific carboxylic acid residues of cyt b5 with lysine residues on cyt c. Site-directed mutagenesis was used to alter the specified acidic residues of cyt b5 to the corresponding amide analogues, which resulted in a lower affinity for complex formation with cyt c. The dissociation of the complex under high pressure resulted in specific volume changes, the magnitude of which reflected the degree of solvation of the acidic residues in the proposed protein-protein interface.     

NMR characterization of surface interactions in the cytochrome b5-cytochrome c complex

The complex formed in solution by native and chemically modified cytochrome c with cytochrome b5 has been studied by 1H and 13C nuclear magnetic resonance spectroscopy (NMR). Contrary to predictions of recent theoretical analysis, 1H NMR spectroscopy indicates that there is no major movement of cytochrome c residue Phe82 on binding to cytochrome b5. The greater resolution provided by 13C NMR spectroscopy permits detection of small perturbations in the environments of cytochrome c residues Ile75 and Ile85 on binding with cytochrome b5, a result that is in agreement with earlier model-building experiments. As individual cytochrome c lysyl residues are resolved in the 1H NMR spectrum of N-acetimidylated cytochrome c, the interaction of this modified protein with cytochrome b5 has been studied to evaluate the number of cytochrome c lysyl residues involved in binding to cytochrome b5. The results of this experiment indicate that at least six lysyl residues are involved, two more than predicted by static model building, which indicates that cytochrome c and cytochrome b5 form two or more structurally similar 1:1 complexes in solution.     

Phosphorylation coupled to the transfer of electrons from glutathione to cytochrome c

Formation of adenosine diphosphate from adenosine monophosphate and inorganic phosphate can be coupled to the oxidation of reduced glutathione by cytochrome c in a reaction which requires oxidized glutathione as a catalyst. The reaction occurs with purified materials in tris(hydroxymethyl)aminomethane buffer and may represent the type reaction for one or more oxidative phosphorylations.     

New light-sensitive cofactor required for oxidation of succinate by Mycobacterium phlei

Irradiation of the electron transport particles of Mycobacterium phlei with light at a wavelength of 360 manometers resulted in a loss of oxidase activities of succinate and the reduced form of nicotinamide adenine dinucleotide. The lesion in the two pathways caused by irradiation of the particles differs. The succinoxidase pathway was more labile to irradiation than the pathway linked to nicotinamide adenine dinucleotide. Restoration of succinoxidase activity (up to 50 to 60 percent) occurred on addition of a thermostable, water-soluble material obtained from Mycobacterium phlei cells or with an extract of mitochondria from boiled rat liver. Other known cofactors, such as flavine adenine dinucleotide, flavine mononucleotide, benzo- and naphthoquinones, as well as sulfhydryl agents, failed to restore succinoxidase activity after irradiation. Water-soluble material from Mycobacterium phlei appears to function between the flavoprotein and cytochrome b on the succinoxidase pathway. In contrast to the requirements for restoration of the pathway linked to nicotinamide adenine dinucleotide, restoration of succinoxidase does not occur with quinones or other cofactors such as flavine adenine dinucleotide.     

Cytochrome a3: destruction by light

Spectroscopic measurements on cultures of Prototheca zopfii irradiated with blue light revealed that inhibition of respiration was accompanied by destruction of cytochrome a(3). One of the three b-type cytochromes and one of the two c-type cytochromes of this organism were also affected. Cytochrome oxidase of yeast (not resolved into the a and a(3) components) and cytochrome a(3) of beef-heart mitochondria were also destroyed by blue light.     

Polymeric structure of spruce lignin

From the Flory-Stockmayer theory and molecular weights of successive fractions of lignin obtained by extraction of spruce wood with a mixture of water, dioxane, and hydrochloric acid and by sulfonation, the average length of the primary chains was estimated to be 18 phenylpropane units. From data on the acid-catalyzed cleavage of model compounds in various solvents the degrees of cross-linking in four extraction processes were calculated. The average degree of cross-linking of intact lignin was found to be 0.277; that is, 5 out of every 18 phenylpropane units bear cross-linking benzyl ether groups. Of the five, three are also etherified at their phenolic ends (B groups), and two are not (X groups).     

L-肉碱与辅酶Q10添加对腹水症肉鸡心肌细胞凋亡及抗氧化能力的影响

为探讨L-肉碱与辅酶Q10单独或共同添加时对腹水症肉鸡心肌细胞凋亡的影响,在饲料中添加100 mg/kg L-肉碱和40 mg/kg辅酶Q10,采用常规温度缓慢降温和低温处理。结果表明:日粮中单独添加辅酶Q10可以显著降低低温组肉鸡36日龄时的红细胞压积(PCV)(0.41 vs.0.31)(P<0.05),单独添加L-肉碱可以显著降低低温组肉鸡42日龄时的腹水心脏指数(AHI)(0.31 vs.0.21)(P<0.05);单独添加L-肉碱或辅酶Q10以及二者同时添加都可以显著降低腹水症的死亡率(P<0.05)。正常肉鸡心肌细胞采用H2O2诱导凋亡时,发现有细胞色素C大量释放到胞浆中,而不采用H2O2诱导凋亡组则没有观察到该现象;腹水症肉鸡心肌细胞不论采用H2O2诱导凋亡与否都发现有细胞色素C释放到胞浆中的现象。但各组Caspase-3活性并没有显著变化,L-肉碱与辅酶Q10同时添加时可显著提高腹水症肉鸡心肌线粒体谷胱甘肽(GSH)含量和血清中抗活性氧能力(A-RC)(P<0.05)。因此肉鸡发生腹水症与心肌细胞凋亡之间存在必然联系,但日粮单独或共同添加L-肉碱与辅酶Q10均能够显著降低肉鸡腹水症的死亡率。     

松材线虫对其携带的一株致病细菌产毒的影响

该文报道了以黑松细胞为材料的一种改进的细胞荧光染色显微生测法.用该方法测定了接种松材线虫虫体上分离到的荧光假单胞GcM5-1A菌株或该菌株和无菌松材线虫混合物接种后的愈伤组织水提物的毒性.结果表明,单独接种无菌松材线虫或单独接种该菌株后的愈伤组织水提液未表现出毒性;而接种无菌松材线虫与该菌株的混合物后的愈伤组织水提液与接种野生松材线虫后的愈伤组织水提液的毒性以及该菌株的NB培养液的无细胞滤液的毒性均很强,并且它们三者之间没有显著差异.该结果说明松材线虫在寄主组织中能促进细菌的产毒.向该菌株的NB培养液的无细胞滤液中添加松材线虫后测定其毒性,结果表明无菌松材线虫对其毒性并无显著影响.实验结果表明松材线虫本身不产生毒素,在荧光假单胞菌培养液的无细胞滤液中加入无菌松材线虫未能显著改变其毒性.      

磁混肥对梨果产量品质及梨树酶活性的研究

磁混肥比混肥和习惯用肥明显增产。其中,以每株施花肥、壮果肥粪水各5kg,50kg和磁混肥1.5kg,2.3kg的产量最高,其糖/酸比值为67.3,叶片中养分N∶P_2O_5∶K_2O=1.0∶0.17∶0.60,磷含量高。日增长体积以每株施花肥、果肥粪水各25kg,50kg和磁混肥0.75kg,1.17kg处理最大,为6.06×10~(-6)mm~3。磁混肥处理SOD酶活力前期强,利于抗衰老,其后逐渐减弱,有利促进梨果成熟。     

Proton magnetic resonance of proteins fully deuterated except for 1H-leucine side chains

The fully deuterated proteins C-phycocyanin, C-phycoerythrin, and cytochrome c have been obtained by biosynthesis with the leucine side chains, and only the leucine side chains, of normal ((1)H) isotopic composition. In these (isotopic hybrid) proteins, proton magnetic resonance analysis shows that the (1)H-leucine side chains are in a variety of environments. During protein biosynthesis, the alpha hydrogen of leucine is exchanged with a hydrogen ((2)H) from the aqueous medium.     

根际促生细菌混合接种对甜樱桃/东北山樱根际微生物区系及根系呼吸的影响

为探讨有益微生物对甜樱桃根系的接种效应,试验采用灌根的方法,研究了从野生东北山樱根际分离筛选出的4株促生细菌,混合接种对甜樱桃/东北山樱根际微生物区系及根系呼吸代谢途径的影响.结果表明:接种促生菌液改变了甜樱桃根际细菌、放线菌及真菌的数量比例,使根际细菌数量显著增加.接种2次,根际细菌增加幅度最大,为对照的3.4倍;接种促生菌液提高了根系活力,接种2次效果最显著,为对照的2.4倍,达到200.4μg/(g·h);接种促生菌液对根系呼吸的基础生化途径与末端氧化电子传递途径运行比例无明显影响,但整体上提高了根系呼吸速率.     

Molecular dynamics of a cytochrome c-cytochrome b5 electron transfer complex

Cytochrome c and cytochrome b5 form an electrostatically associated electron transfer complex. Computer models of this and related complexes that were generated by docking the x-ray structures of the individual proteins have provided insight into the specificity and mechanism of electron transfer reactions. Previous static modeling studies were extended by molecular dynamics simulations of a cytochrome c-cytochrome b5 intermolecular complex. The simulations indicate that electrostatic interactions at the molecular interface results in a flexible association complex that samples alternative interheme geometries and molecular conformations. Many of these transient geometries appear to be more favorable for electron transfer than those formed in the initial model complex. Of particular interest is a conformational change that occurred in phenylalanine 82 of cytochrome c that allowed the phenyl side chain to bridge the two cytochrome heme groups.     

Biosynthesis of hemoglobin Ann Arbor: evidence for catabolic and feedback regulation

Hemoglobin Ann Arbor, in which arginine replaces leucine in position 80 of the a chain, occurs in aflected individuals in low proportion to hemoglobin A. Biosynthetic studies were perforined on reticulocytes of a patient heterozygous for this hemoglobin. These studies suggested that the low percentage of hemoglobin Ann Arbor is prinlarily due to preferential destruction of the abnormal component. The reduced concentration of alpha Ann Arbor chains was also reflected in a decreased synthesis of normal beta chains.     

Structure of the cytochrome b6f complex of oxygenic photosynthesis: tuning the cavity

The cytochrome b6f complex provides the electronic connection between the photosystem I and photosystem II reaction centers of oxygenic photosynthesis and generates a transmembrane electrochemical proton gradient for adenosine triphosphate synthesis. A 3.0 angstrom crystal structure of the dimeric b6f complex from the thermophilic cyanobacterium Mastigocladus laminosus reveals a large quinone exchange cavity, stabilized by lipid, in which plastoquinone, a quinone-analog inhibitor, and a novel heme are bound. The core of the b6f complex is similar to the analogous respiratory cytochrome bc1 complex, but the domain arrangement outside the core and the complement of prosthetic groups are strikingly different. The motion of the Rieske iron-sulfur protein extrinsic domain, essential for electron transfer, must also be different in the b6f complex.     

Transport studies in bacterial membrane vesicles

The use of bacterial membrane vesicles as an experimental system for the study of active transport has been discussed. Vesicles are prepared from osmotically sensitized bacteria, and consist of osmotically intact, membranebound sacs without internal structure. They retain litle or no cytoplasm. Under appropriate conditions, these vesicles catalyze the transport of a variety of solutes at rates which are comparable, in many cases, to those of intact cells. Two general types of transport systems have been elucidated in the vesicle system: (i) group translocation systems which catalyze vectorial covalent reactions; and (ii) respirationlinked transport systems that catalyze the active transport of a whole range of metabolites against an electrochemical or osmotic gradient. In E. coli membrane vesicles, the respiration-linked transport systems are coupled primarily to the oxidation of (D)-lactate to pyruvate, catalyzed by a flavin-linked, membrane-bound (D)-lactate dehydrogenase which has been purified to homogeneity. Electrons derived from (D)-lactate or certain artificial electron donors are transferred to oxygen by means of a membrane-bound respiratory chain, and respiration is coupled to active transport within a segment of the respiratory chain between the primary dehydrogenase and cytochrome. b(l). The great majority of the individual membrane vesicles in the population catalyze active transport, and the generation or hydtolysis of ATP is not involved. Under anaerobic conditions, fumarate or nitrate can be utilized in place of oxygen as terminal electron acceptors. With the exception that (D)-lactate is not always the most effective electron donor for active transport, vesicles prepared from a number of other organisms catalyze transport in a similar manner. Fluorescent dansylgalactosides are useful molecular probes of active transport in the vesicle system. These compounds are competitive inhibitors of beta-galactoside transport, but are not transported themselves. Fluorescence studies indicate that the lac carrier protein constitutes approximately 3 to 6 percent of the total membrane protein, and that it is not accessible to the external medium unless the membrane is "energized." Thus, energy is coupled to one of the initial steps in the transport process. Studies with a photoaffinity-labeled galactoside provide independent support for this conclusion. When membrane vesicles prepared from a (D)-lactate dehydrogenase mutant of E. coli are treated with (D)-lactate dehydrogenase, the enzyme binds to the vesicles and they regain the capacity to catalyze (D)-lactate oxidation and (D)-lactate-dependent active transport. The maximal specific transport activity obtained in the reconstituted system is similar in magnitude to that of wildtype vesicles. Titration studies with dansylgalactoside demonstrate that there is at least a seven- to eightfold excess of lac carrier protein relative to (D)-lactate dehydrogenase. Evidence is presented indicating that the enzyme is bound to the inner surface of native membrane vesicles and to the outer surface of reconstituted vesicles, and that the flavin coenzyme moiety is critically involved in binding. Possible mechanisms of respirationlinked active transport are discussed.