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1.
The genes encoding the α1 and β subunits of voltage-sensitive calcium channel were mapped in the mouse by analysis of the progeny of two multilocus crosses. The α1, β2, and β4 subunit genes, termed Cchna1, Cchb2, and Cchb4, are located at different sites on proximal Chr 2, while the β3 subunit gene Cchb3 maps to Chr 15 near Wnt1. These results together with previous mapping data indicate that the calcium channel genes are dispersed in the mouse genome, unlike the sodium channel genes, which are clustered. 相似文献
2.
3.
On the relationship between leaf anatomy and CO2 diffusion through the mesophyll of hypostomatous leaves 总被引:11,自引:8,他引:3
J. P. SYVERTSEN J. LLOYD C. McCONCHIE P. E. KRIEDEMANN G. D. FARQUHAR 《Plant, cell & environment》1995,18(2):149-157
Internal conductances to CO2 transfer from the stomatal cavity to sites of carboxylation (gi) in hypostomatous sun-and shade-grown leaves of citrus, peach and Macadamia trees (Lloyd et al. 1992) were related to anatomical characteristics of mesophyll tissues. There was a consistent relationship between absorptance of photosynthetically active radiation and chlorophyll concentration (mmol m?2) for all leaves, including sclerophyllous Macadamia, whose transmittance was high despite its relatively thick leaves. In thin peach leaves, which had high gi, the chloro-plast volume and mesophyll surface area exposed to intercellular air spaces (ias) per unit leaf area were similar to those in the thicker leaves of the evergreen species. Peach leaves, however, had the lowest leaf dry weight per area (D/a), the lowest tissue density (Td) and the highest chloro-plast surface area (Sc) exposed to ias. There were negative correlations between gi and leaf thickness or D/a, but positive correlations between gi and Sc or Sc/Td. We developed a one-dimensional diffusion model which partitioned gi into a gaseous diffusion conductance through the ias (gias) plus a liquid-phase conductance through mesophyll cell walls (gcw). The model accounted for a significant amount of variation (r2=0.80) in measured gi by incorporating both components. The gias component was related to the one-dimensional path-length for diffusion across the mesophyll and so was greater in thinner peach leaves than in leaves of evergreen species. The gcw component was related to tissue density and to the degree of chloroplast exposure to the ias. Thus the negative correlations between gi and leaf thickness or D/a related to gias whereas positive correlations between gi and Sc or Sc/Td, related to gcw. The gcw was consistently lower than gias, and thus represented a greater constraint on CO2 diffusion in the mesophylls of these hypostomatous species. 相似文献
4.
Lysozyme, cytochrome c, poly(l-lysine), myelin basic protein and ribonuclease were used to form multilayer dispersions containing about 50% protein (by weight) with bovine brain diacyl phosphatidylserine (PS). 31P nuclear magnetic resonance shift anisotropies, spin-spin (T2) and spin-lattice (T1) relaxation times for the lipid headgroup phosphorus were measured at 36.44 MHz. At pH 7.5, lysozyme, cytochrome c, poly(l-lysine) and ribonuclease were shown to increase the chemical shift anisotropy of PS by between 12–20%. Myelin basic protein altered the shape of the phosphate resonance, suggesting the presence of two lipid components, one of which had a modified headgroup conformation. The presence of cytochrome c led to the formation of a narrow spike at the isotropic shift position of the spectrum. Of the various proteins or peptides we have studied, only poly(l-lysine) and cytochrome c had any effect on the T1 of PS (1050 ms). Both caused a 20–30% decrease in T1 of the lamellar-phase phosphate peak. The narrow peak in the presence of cytochrome c had a very short T1 of 156 ms. The possibility is considered that the cytochrome Fe3+ contributes to the phosphate relaxation in this case. The effect of all proteins on the T2 of the phosphorus resonance was to cause an increase from the value for pure PS (1.6 ms) to between 2 and 5 ms. The results obtained with proteins are compared with the effects of small ions and intrinsic membrane proteins on the order and motion of the headgroups of lipids in bilayers. 相似文献
5.
To refine the linkage map of distal mouse Chromosome 12, we have identified DNA restriction fragment variants associated with a creatine kinase gene (Ck-3), the Akt proto-oncogene, an Abelson proviral integration site (D12N1), and the immunoglobulin heavy chain VH3609 variable region family (Igh-V36). The patterns of inheritance of these markers in backcross progeny and recombinant inbred mouse strains allowed their localization with respect to previously mapped genes to yield the linkage map: Aat-15.8 cM-Ck-3-0.9 cM-(Crip, Akt, Igh-C)-0.3 cM-(D12N1, Igh-V). This map confirms genetically the localization of the Igh-V gene complex distal to Igh-C on the chromosome. It differs from previous maps in placing D12N1 distal to Igh-C, and in suggesting that the Igh-V gene complex spans less than one centiMorgan (cM).Other DNA sequence variants detected with the creatine kinase probe allowed definition of four additional genetic loci: Ck-1 near Lmyc-1 on Chromosome 4; Ck-2 between Upg-1 and Hprt-ps1 (D17Rp10) on distal Chromosome 17; Ck-4 near Mpmv-17 and Mls-3 on Chromosome 16; and Ck-5 near Hba on Chromosome 11. 相似文献
6.
Discovery and characterization of electron transfer proteins in the photosynthetic bacteria 总被引:4,自引:0,他引:4
Research on photosynthetic electron transfer closely parallels that of other electron transfer pathways and in many cases
they overlap. Thus, the first bacterial cytochrome to be characterized, called cytochrome c
2, is commonly found in non-sulfur purple photosynthetic bacteria and is a close homolog of mitochondrial cytochrome c. The cytochrome bc
1 complex is an integral part of photosynthetic electron transfer yet, like cytochrome c
2, was first recognized as a respiratory component. Cytochromes c
2 mediate electron transfer between the cytochrome bc
1 complex and photosynthetic reaction centers and cytochrome a-type oxidases. Not all photosynthetic bacteria contain cytochrome c
2; instead it is thought that HiPIP, auracyanin, Halorhodospira cytochrome c551, Chlorobium cytochrome c555, and cytochrome c
8 may function in a similar manner as photosynthetic electron carriers between the cytochrome bc
1 complex and reaction centers. More often than not, the soluble or periplasmic mediators do not interact directly with the
reaction center bacteriochlorophyll, but require the presence of membrane-bound intermediates: a tetraheme cytochrome c in purple bacteria and a monoheme cytochrome c in green bacteria. Cyclic electron transfer in photosynthesis requires that the redox potential of the system be delicately
poised for optimum efficiency. In fact, lack of redox poise may be one of the defects in the aerobic phototrophic bacteria.
Thus, large concentrations of cytochromes c
2 and c′ may additionally poise the redox potential of the cyclic photosystem of purple bacteria. Other cytochromes, such as flavocytochrome
c (FCSD or SoxEF) and cytochrome c551 (SoxA), may feed electrons from sulfide, sulfur, and thiosulfate into the photosynthetic pathways via the same soluble
carriers as are part of the cyclic system.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
S. Benini Marco Borsari S. Ciurli Alexander Dikiy M. Lamborghini 《Journal of biological inorganic chemistry》1998,3(4):371-382
Direct cyclic voltammetry and 1H NMR spectroscopy have been combined to investigate the electrochemical and spectroscopic properties of cytochrome c
553 isolated from the alkaliphilic soil bacterium Bacillus pasteurii. A quasi-reversible diffusion-controlled redox process is exhibited by cytochrome c
553 at a pyrolitic graphite edge microelectrode. The temperature dependence of the reduction potential, measured using a non-isothermal
electrochemical cell, revealed a discontinuity at 308 K. The thermodynamic parameters determined in the low-temperature range
(275–308 K;ΔS°′=–162.7±1.2 J mol–1 K–1, ΔH°′=–53.0±0.5 kJ mol–1, ΔG°′=–4.5±0.1 kJ mol–1, E°′=+47.0±0.6 mV) indicate the presence of large enthalpic and entropic effects, leading, respectively, to stabilization and
destabilization of the reduced form of cytochrome c
553. Both effects are more accentuated in the high-temperature range (308–323 K;ΔS°′=–294.1±8.4 J mol–1 K–1, ΔH°′=–93.4±3.1 kJ mol–1, ΔG°′=–5.8±0.6 kJ mol–1, E°′=+60.3±5.8 mV), with the net result being a slight increase of the standard reduction potential. These thermodynamic parameters
are interpreted using the compensation theory of hydration of biopolymers as indicating the extrusion, upon reduction, of
water molecules from the hydration sphere of the cytochrome. The low-T and high-T conformers differ by the number of water molecules in the solvation sphere: in the high-T conformer, the number of water molecules extruded upon reduction increases, as compared to the low-T conformer. The ionic strength dependence of the reduction potential at 298 K, treated within the frame of extended Debye-Hückel
theory, yields values of E
°′
(I=0)
=–25.4±1.4 mV, z
red=–11.3, and z
ox=–10.3. The pH dependence of the reduction potential at 298 K shows a plateau in the pH range 7–10 and an increase at more
acidic pH, allowing the calculation of pK
O=5.5 and pK
R=5.7, together with the estimate of the reduction potentials of completely protonated (+71 mV) and deprotonated (+58 mV) forms
of cytochrome c
553. 1H NMR spectra of the oxidized paramagnetic cytochrome c
553 indicate the presence of a His-Met axial coordination of the low-spin (S=1/2) heme iron, which is maintained in the temperature interval 288–340 K at pH 7 and in the pH range 4.8–10.0 at 298 K.
The temperature dependence of the hyperfine-shifted signals shows both Curie-type and anti-Curie-type behavior, with marked
deviations from linearity, interpreted as indicating the presence of a fast equilibrium between the low-T and high-T conformers, having slightly different heme electronic structures resulting from the T-induced conformational change. Increasing the NaCl concentration in the range 0–0.2 M causes a slight change of the 1H NMR chemical shifts of the hyperfine-shifted signals, with no influence on their linewidth. The calculated lower limit value
of the apparent affinity constant for specific ion binding is estimated as 5.2±1.1 M–1. The pH dependence of the isotropically shifted 1H NMR signals of the oxidized cytochrome displays at least one ionization step with pK
O=5.7. The thermodynamic and spectroscopic data indicate a large solvent-derived entropic effect as the main cause for the
observed low reduction potential of B. pasteurii cytochrome c
553.
Received: 9 January 1998 / Accepted: 8 April 1998 相似文献
8.
A Gram-negative, non-motile, non-endospore-forming bacterial strain, designated DPSR-4T, was isolated from a tidal flat sediment on the southern coast of Korea. Strain DPSR-4T grew optimally at 25–30°C, at pH 7.0–7.5 and in the presence of 2% (w/v) NaCl. A Neighbour-Joining phylogenetic tree based
on 16S rRNA gene sequences revealed that strain DPSR-4T clustered with Salinimonas
chungwhensis BH030046T by a high bootstrap resampling value of 99.7%. Strain DPSR-4T exhibited 96.2% 16S rRNA gene sequence similarity to that of S. chungwhensis BH030046T and 93.7–96.6% sequence similarity to the sequences of type strains of Alteromonas species. Strain DPSR-4T contained Q-8 as the predominant ubiquinone and iso-C15:0 2-OH and/or C16:1
ω7c, C16:0 and C18:1
ω7c as the major fatty acids. The major polar lipids detected in strain DPSR-4T and S. chungwhensis KCTC 12239T were phosphatidylglycerol, phosphatidylethanolamine and an unidentified phospholipid. The DNA G+C content was 53.4 mol%.
Differential phenotypic properties and phylogenetic distinctiveness of strain DPSR-4T demonstrated that this strain is distinguishable from the sole recognized species of the genus Salinimonas, S. chungwhensis. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain DPSR-4T is considered to represent a novel species of the genus Salinimonas, for which the name Salinimonas lutimaris sp. nov. is proposed. The type strain is DPSR-4T (KCTC 23464T, CCUG 60743T). 相似文献
9.
Bradyrhizobium japonicum possesses a mitochondria-like respiratory chain terminating with an aa
3-type cytochrome c oxidase. The gene for subunit I of this enzyme (coxA) had been identified and cloned previously via heterologous hybridization using a Paracoccus denitrificans DNA probe. In the course of these studies, another B. japonicum DNA region was discovered which apparently encoded a second terminal oxidase that was different from cytochrome aa
3 but also belonged to the superfamily of heme/copper oxidases. Nucleotide sequence analysis revealed a cluster of at least four genes, coxMNOP, organized most probably in an operon. The predicted coxM gene product shared significant similarity with subunit II of cytochrome c oxidases from other organisms: in particular, all of the proposed CuA ligands were conserved as well as three of the four acidic amino acid residues that might be involved in the binding of cytochrome c. The coxN gene encoded a polypeptide with about 40% sequence identity with subunit I representatives including the previously found CoxA protein: the six presumed histidine ligands of the prosthetic groups (two hemes and CuB) were strictly conserved. A remarkable feature of the DNA seqence was the presence of two genes, coxO and coxP, whose products were both homologous to subunit III proteins. A B.japonicum coxN mutant strain was created by marker exchange mutagenesis which, however, exhibited no obvious defects in free-living, aerobic growth or in root nodule symbiosis with soybean. This shows that the coxMNOP genes are not essential for respiration in the N2 fixing bacteroid.Abbreviations ORF
open reading frame
- TMPD
N,N,N',N'-tetramethyl-p-phenylenediamine 相似文献
10.
Tracy M. Josephs Moira E. Hibbs Lily Ong Ian M. Morison Elizabeth C. Ledgerwood 《PloS one》2015,10(6)
The naturally occurring human cytochrome c variant (G41S) is associated with a mild autosomal dominant thrombocytopenia (Thrombocytopenia Cargeeg) caused by dysregulation of platelet production. The molecular basis of the platelet production defect is unknown. Despite high conservation of cytochrome c between human and mouse (91.4% identity), introducing the G41S mutation into mouse cytochrome c in a knockin mouse (Cycs
G41S/G41S) did not recapitulate the low platelet phenotype of Thrombocytopenia Cargeeg. While investigating the cause of this disparity we found a lack of conservation of the functional impact of cytochrome c mutations on caspase activation across species. Mutation of cytochrome c at residue 41 has distinct effects on the ability of cytochrome c to activate caspases depending on the species of both the cytochrome c and its binding partner Apaf-1. In contrast to our previous results showing the G41S mutation increases the ability of human cytochrome c to activate caspases, here we find this activity is decreased in mouse G41S cytochrome c. Additionally unlike wildtype human cytochrome c, G41S cytochrome c is unable to activate caspases in Xenopus embryo extracts. Taken together these results demonstrate a previously unreported species-specific component to the interaction of cytochrome c with Apaf-1. This suggests that the electrostatic interaction between cytochrome c and Apaf-1 is not the sole determinant of binding, with additional factors controlling binding specificity and affinity. These results have important implications for studies of the effects of cytochrome c mutations on the intrinsic apoptosis pathway. 相似文献
11.
Mapping of the structural gene for S-adenosyl homocysteine hydrolase to mouse Chromosome 2, and related sequences to Chromosomes 8 and X 总被引:1,自引:0,他引:1
Alison Pilz Paul Le Tissier Heather Moseley Jo Peters Cathy Abbott 《Mammalian genome》1992,3(11):633-636
Comparative mapping studies in human and mouse have shown that, to date, human Chromosome (Chr) 20 is completely syntenic with distal mouse Chr 2. The structural locus for S-adenosyl-l-homocysteine hydrolase (EC 3.3.1.1) in human, AHCY, maps to 20 qterq13.1, and we report here that the homologous locus in the mouse, Ahcy, maps to distal mouse Chr 2 with gene order Pcna-Ahcy-Ada. Analysis of 123 progeny of an interspecific backcross between a laboratory stock, AN, and Mus spretus using a rat cDNA probe revealed the presence of at least two other Ahcy-related sequences segregating independently in the mouse genome. One, Ahcy-rs1, was mapped to Chr 8 in the BXH recombinant inbred strains, and the other, Ahcy-rs2, shows a pattern of inheritance consistent with X-linkage. 相似文献
12.
Roger H. Reeves Michael R. Crowley Walton S. Moseley Michael F. Seldin 《Mammalian genome》1991,1(3):158-164
One hundred fourteen progeny from an interspecific backcross between laboratory mice and M. spretus were typed for six markers spanning most of mouse Chromosome (Chr) 16. Additional maps of 9–10 markers of this chromosome were derived from analysis of over 500 progeny from four backcrosses between inbred laboratory strains and members of the Mus musculus group, M.m. musculus and M.m. molossinus (subspecies). The results of these analyses confirmed the gene order: (CEN)-Prm-1/Prm-2-Igl-1-Smst-Mtv-6-Gap43-Pit-1(dw)-D21S16h-App-Sod-1-Ets-2-Mx. Maps produced from these five crosses were of similar lengths, but recombination in several regions was affected by sex of the F1 parent or by the combination of strains used in the cross. As reported previously, recombination frequencies were elevated significantly at the distal end of the chromosome in a cross using F1 males. The male map showed significant compression in the interval Smst to Gap43. Both male and female intersubspecific maps were expanded near the proximal and distal ends of the chromosome relative to the interspecific cross. The spretus cross was compressed in the proximal interval, Prm-1-Igl-1-Smst, and was slightly expanded in the Smst-Gap43 interval, relative to intersubspecific crosses using F1 females. Female intersubspecific maps were expanded about 50% near the distal end of the chromosome when compared to the interspecific cross. The expansion or compression of maps using different strain or sex combinations has implications for the efficient production of high resolution recombinational maps of the mouse genome. 相似文献
13.
THE EFFECT OF ESTRADIOL ON THE CELL KINETICS IN THE UTERINE AND CERVICAL EPITHELIUM OF NEONATAL MICE
The effect of estradiol-17β on the length of the various phases of the cell cycle was studied in the neonatal mouse uterine, and cervical epithelium. A double labelling method was used, and in addition labelled mitoses were counted. In the uterus proper, estradiol shortens the length of the total cell cycle, Tc, from 17-9 hr to 15-7 hr, and the duration of S phase, Ts, from 6–7 to 5-1 hr 6 hr after estradiol treatment. 12 hr after estradiol treatment, Tc is shortened to 7-4 hr and Ts to 4–5 hr. The shortening of Tc at 12 hr is mainly due to an effect on TG1, which is shortened from 8–55 hr in untreated animals to 1–8 hr in estradiol treated animals. The Tc of cervix epithelium cells in untreated animals was found to be 21-8 hr. After treating the mice for 6 hr with estradiol the Tc was now increased to 47 hr and further to 61 -2 hr following 12 hr treatment with the hormone. Ts increases from 8-3 hr to 15-2 hr following 6 hr estradiol treatment, and to 15-4 hr after 12 hr treatment. The effect is most pronounced in TG1, which is lengthened from 10–95 hr in untreated animals to 28-1 hr and 43 hr, respectively, in animals treated for either 6 or 12 hr with estradiol. 相似文献
14.
Formation of several bacterial c-type cytochromes requires a novel membrane-anchored protein that faces the periplasm 总被引:14,自引:2,他引:12
We report here the discovery of a novel bacterial gene (cycH) whose product is involved in the biogenesis of most of the cellular cytochromes c. The cycH gene was detected in the course of characterizing a cytochrome oxidase-deficient Bradyrhizobium japonicum Tn5 mutant (strain CO×3) in which the transposon insertion disrupted cycH. Ali of the c-type cytochromes detectable in aerobically grown B. Japonicum wild-type cells were absent in the C0X3 mutant, with the exception of cytochrome c1. A secondary phenotypic effect was the spectroscopic absence of the aa3-type cytochrome c oxidase. The nucleotide sequence of the cloned wild-type cycH gene predicted a membrane-bound 369-amino-acid protein with an Mr of 39727. Results from studies on its membrane topology suggested that approximately 110 N-terminal amino acids are involved in anchoring the protein in the membrane, whereas the remaining two-thirds of the protein are exposed to the periplasm. We postulate that the CycH protein plays an essential role in an as yet unidentified periplasmic step in the biogenesis of holocytochromes c, except that of cytochrome c1. 相似文献
15.
Myakoshina Yu. A. Punina E. O. Grif V. G. Rodionov A. V. 《Russian Journal of Genetics》2004,40(8):882-891
Chromosome banding with nucleotide base-specific fluorochromes chromomycin A3 (CMA) and Hoechst 33258 (H33258) was used to study the karyotypes and to construct cytological maps for diploidTrillium camschatcense(2n = 10), tetraploid T. tschonoskii(2n = 20), hexaploidT. rhombifolium (2n = 30), and a triploid T. camschatcense × T. tschonoskii hybrid (T. × hagae, 2n = 15). With H33258, species- and genome-specific patterns with numerous AT-rich heterochromatin bands were obtained for each of the four forms; CMA revealed a few small, mostly telomeric GC-rich bands. In T. tschonoskii, the two subgenomes were similar to each other and differed from the T. camschatcense genome; on this evidence, the species was considered to be a segmental allotetraploid. InT. ×hagae, one T. camschatcense and both T. tschonoskii subgenomes were identified. The subgenomes of T. rhombifoliumonly partly corresponded to the T. camschatcense and T. tschonoskii genomes, in contrast to the morphologically identical Japanese species T. hagae. This was assumed to indicate that allohexaploids T. rhombifolium and T. hagae originated independently at different times; i.e., their origin is polyphyletic. Based on the chromosome maps, a new nomenclature was proposed for theTrillium genomes examined: K1K1 for T. camschatcense,T1T1T2T2 for T. tschonoskii,K1T1T2 for T. × hagae, and K1RK1RT1RT1RT2RT2R for T. rhombifolium. 相似文献
16.
Structure and Sequence Conservation of hao Cluster Genes of Autotrophic Ammonia-Oxidizing Bacteria: Evidence for Their Evolutionary History 总被引:2,自引:0,他引:2
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Comparison of the organization and sequence of the hao (hydroxylamine oxidoreductase) gene clusters from the gammaproteobacterial autotrophic ammonia-oxidizing bacterium (aAOB) Nitrosococcus oceani and the betaproteobacterial aAOB Nitrosospira multiformis and Nitrosomonas europaea revealed a highly conserved gene cluster encoding the following proteins: hao, hydroxylamine oxidoreductase; orf2, a putative protein; cycA, cytochrome c554; and cycB, cytochrome cm552. The deduced protein sequences of HAO, c554, and cm552 were highly similar in all aAOB despite their differences in species evolution and codon usage. Phylogenetic inference revealed a broad family of multi-c-heme proteins, including HAO, the pentaheme nitrite reductase, and tetrathionate reductase. The c-hemes of this group also have a nearly identical geometry of heme orientation, which has remained conserved during divergent evolution of function. High sequence similarity is also seen within a protein family, including cytochromes cm552, NrfH/B, and NapC/NirT. It is proposed that the hydroxylamine oxidation pathway evolved from a nitrite reduction pathway involved in anaerobic respiration (denitrification) during the radiation of the Proteobacteria. Conservation of the hydroxylamine oxidation module was maintained by functional pressure, and the module expanded into two separate narrow taxa after a lateral gene transfer event between gamma- and betaproteobacterial ancestors of extant aAOB. HAO-encoding genes were also found in six non-aAOB, either singly or tandemly arranged with an orf2 gene, whereas a c554 gene was lacking. The conservation of the hao gene cluster in general and the uniqueness of the c554 gene in particular make it a suitable target for the design of primers and probes useful for molecular ecology approaches to detect aAOB. 相似文献
17.
Lakshmi KV Reifler MJ Chisholm DA Wang JY Diner BA Brudvig GW 《Photosynthesis research》2002,72(2):175-189
The Mn4 cluster of PS II advances through a series of oxidation states (S states) that catalyze the breakdown of water to dioxygen
in the oxygen-evolving complex. The present study describes the engineering and purification of highly active PS II complexes
from mesophilic His-tagged Synechocystis PCC 6803 and purification of PS II core complexes from thermophilic wild-type Synechococcus lividus with high levels of the extrinsic polypeptide, cytochrome c
550. The g = 4.1 S2 state EPR signal, previously not characterized in untreated cyanobacterial PS II, is detected in high yields in these PS
II preparations. We present a complete characterization of the g = 4.1 state in cyanobacterial His-tagged Synechocystis PCC 6803 PS II and S. lividus PS II. Also presented are a determination of the stoichiometry of cytochrome c
550 bound to His-tagged Synechocystis PCC 6803 PS II and analytical ultracentrifugation results which indicate that cytochrome c
550 is a monomer in solution. The temperature-dependent multiline to g = 4.1 EPR signal conversion observed for the S2 state in cyanobacterial PS II with high cytochrome c
550 content is very similar to that previously found for spinach PS II. In spinach PS II, the formation of the S2 state g = 4.1 EPR signal has been found to correlate with the binding of the extrinsic 17 and 23 kDa polypeptides. The finding of
a similar correlation in cyanobacterial PS II with the binding of cytochrome c
550 suggests a functional homology between cytochrome c
550 and the 17 and 23 kDa extrinsic proteins of spinach PS II.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
The effect of solvent viscosity (ηs) and temperature (T) on the shape of the concentration dependence of the principal and total recoils in creep-recovery viscoelastometry experiments has been studied for T4 DNA solutions. The range of DNA concentration (c) was 2 – 40 μg/ml; glycerol, 70–80% v/v, sucrose, 60% v/v; NaCl, 5 mM – 1M; and T, 275 – 323 K. A linear proportionality between recoil and c was obtained at high ηs/T. At low ηs/T, the c-dependence was nonlinear, approaching saturation at higher c. At low c, the slope of both curves was the same. Transition between “linear” and “nonlinear” values occurred over a narrow range of ηs/T (a width of 1–5 K if ηs/T was changed by varying T). (ηs/T)tr, the midpoint of the transition, was independent of solvent properties other than viscosity. Also, (ηs/T)tr increased with c. For a given c, ηs/T values above this transitional value yield linear behavior; below this, nonlinear behavior. The ratio of linear to nonlinear recoil values is a linear function of c with Kc, the slope of this dependence, independent of ηs and T. A kinetic model for the observed nonlinearity of recoil with c is presented. It explains the independence of Kc on ηs and T. An attempt has been made to explain the linear–nonlinear transitions by comparison of τ1 and TR, the lifetime of the contact points of the polymer network in the de Gennes theory. The nonlinear values are consistent with a pseudogel that exists when τ1 < TR. At τ1 > TR, the DNA behavior is similar to that in dilute solutions (linear values). Thus, the condition for transition is τ1 = TR. However, some unsolved problems remain. 相似文献
19.
《FEMS microbiology letters》1998,167(2):171-177
The sequence of the cyc1 gene encoding the Thiobacillus ferrooxidans ATCC 33020 c552 cytochrome, shows that this cytochrome is a 21-kDa periplasmic c4-type cytochrome containing two similar monohaem domains. The kinetics of reduction and the fact that cytochromes c4 are considered to be physiological electron donors of cytochrome oxidases suggest that the last steps of the iron respiratory chain are: rusticyanin→cytochrome c4→cytochrome oxidase. In Thiobacillus ferrooxidans, cyc1 is co-transcribed with the cyc2 gene, encoding a high-molecular-mass monohaem cytochrome c. This suggests that the cytochromes encoded by these genes belong to the same electron transfer chain. 相似文献
20.
A transposon Tn5 mutant of Paracoccus denitrificans, DP108, was incapable of anaerobic or methylotrophic growth and scored negative in the Nadi cytochrome c oxidase test. P. denitrificans DP108 grown aerobically on succinate or choline was devoid of soluble c-type cytochromes and accumulated periplasmic apocytochrome C550, but the membrane-bound holocytochromes c1 and C552 were present at 5-10% of the levels observed in wild-type ceils, DP108 genomic DNA flanking the site of Tn5 insertion was cloned by marker rescue and used to probe a P. denitrificans wild-type DNA library. A hybridizing 3.05 kb Bam HI fragment capable of complementing the DP108 mutation was isolated and a 2.05 kb region of this was sequenced. One major open reading frame equivalent to 413 amino acids was identified, the predicted product of which was similar (33% identity, 55% similarity) to the predicted product of the cycH gene previously identified in Bradyrhizobium japonicum. Similarity of the two cycH gene products to the predicted products of two Escherichia coli genes, nrfG and yejP, was also detected. Significant differences between the phenotypes of P. denitrificans DPI08 and the B. japonicum cycH mutant C0X3, especially with respect to cytochrome c1 synthesis, suggest that the cycH gene product may be an assembly factor. 相似文献