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51.
52.
Summary Sequence-specific 1H and 15N resonance assignments have been made for 137 of the 146 nonprolyl residues in oxidized Desulfovibrio desulfuricans [Essex 6] flavodoxin. Assignments were obtained by a concerted analysis of the heteronuclear three-dimensional 1H-15N NOESY-HMQC and TOCSY-HMQC data sets, recorded on uniformly 15N-enriched protein at 300 K. Numerous side-chain resonances have been partially or fully assigned. Residues with overlapping 1HN chemical shifts were resolved by a three-dimensional 1H-15N HMQC-NOESY-HMQC spectrum. Medium-and long-range NOEs, 3JNH
coupling constants, and 1HN exchange data indicate a secondary structure consisting of five parallel -strands and four -helices with a topology similar to that of Desulfovibrio vulgaris [Hidenborough] flavodoxin. Prolines at positions 106 and 134, which are not conserved in D. vulgaris flavodoxin, contort the two C-terminal -helices.Abbreviations CSI
chemical shift index
- DQF-COSY
double-quantum-filtered correlation spectroscopy
- DIPSI
decoupling in the presence of scalar interactions
- FMN
flavin mononucleotide
- GARP
globally optimized alternating phase rectangular pulse
- HMQC
heteronuclear multiple-quantum coherence
- HSQC
heteronuclear single-quantum coherence
- NOE
nuclear Overhauser effect
- NOESY
nuclear Overhauser enhancement spectroscopy
- TOCSY
total correlation spectroscopy
- TPPI
time-proportional phase increments
- TSP
3-(trimethylsilyl)propionic-2,2,3,3-d
4 acid, sodium salt 相似文献
53.
The lozenge locus is genetically complex, containing two functionally distinct units, cistrons A and B, that influence the structure of
the compound eye. Extreme mutations of either cistron produce adult phenotypes that share similarities and that have striking
differences. We have analyzed the expression of several developmentally important eye genes including boss, scabrous, rhomboid, seven-up, and Bar in lozenge mutant backgrounds representing both cistrons. This analysis follows the progressive recruitment of photoreceptor neurons
during eye development and has confirmed that the initial development of photoreceptors is normal up to the five cell precluster
stage (R8, R2/5 and R3/4). However, when lozenge is mutant, further eye development is perturbed. As cells R1, R6 and R7 are recruited, patterns of gene expression for seven-up and Bar become abnormal. We have also characterized the expression of two different enhancer trap alleles of lozenge. The lozenge product(s) appear to be first expressed in the eye disc in undifferentiated cells shortly after the five cell precluster forms.
Then, as distinct cells are recruited to a fate, lozenge expression persists and is refined in those cells. Our data suggests that lozenge functions in cone cells and pigment cells as well as in specific glia. With respect to photoreceptor neurons, lozenge biases the developmental potential of cells R1, R6 and R7, by directly influencing the expression of genes important for establishing
cell fate.
Received: 26 July 1996 / Accepted: 6 January 1997 相似文献
54.
Medicago truncatula (barrel medic) is an annual legume of agricultural and biological interest. In this report regeneration from isolated mesophyll protoplasts is described. A specifically developed, highly regenerable seed line is essential for regeneration. Other critical requirements for regeneration are the starting plant material, the use of agarose droplets incubated in a shallow layer of liquid medium, and protoplast density. Plants are grown in controlled environment conditions. Protoplasts are purified using a Percoll-based flotation procedure, then embedded in 100 l agarose droplets containing a basal medium plus 25 M NAA and 4 M BAP (the same medium as in the surrounding shallow liquid layer) to induce protoplast division. A protoplast density of 6–8×105 ml–1 is required for maximum colony formation. M. truncatula plants previously transformed for kanamycin resistance yielded embryogenic callus and also regenerated plants. Protoplasts from other annual Medicago (M.intertexta and M.scutellata) species readily form calli by the procedure we have described.Abbreviations BAP
6-benzylaminopurine
- 2,4-D
2,4-dichlorophenoxyacetic acid
- NAA
1-naphthaleneacetic acid 相似文献
55.
S Mac Neil S W Walker H J Senior A Pollock B L Brown S S Bleehen D S Munro S Tomlinson 《The Biochemical journal》1984,224(2):453-460
Calmodulin antagonists inhibited hormone-stimulated cyclic AMP accumulation in both cultured cells and cell lysates of mouse B16 melanoma. Particulate preparations of B16 melanoma contained 34-45% of total cell calmodulin, which could not be dissociated by extensive washing irrespective of the presence of EGTA in the buffer. The adenylate cyclase activity in such preparations was unaffected by the addition of exogenous calmodulin. However, the rare-earth-metal ion La3+, which can mimic or replace Ca2+ in many systems, produced an immediate inhibition of agonist-stimulated adenylate cyclase activity and preincubation of particulate preparations was La3+ followed by washing with La3+-free buffer dissociated calmodulin (96% loss) from particulate preparations. The loss of calmodulin from particulate preparations was associated with a decrease in agonist responsiveness (74%) and a marked change in the Ca2+-sensitivity of the enzyme, low concentrations of calcium (approx. 10 nM) now failing to stimulate enzyme activity, high concentrations of calcium (greater than or equal to 100 nM) producing greater-than-normal inhibition of enzyme activity. Direct activation of adenylate cyclase by the addition of pure calmodulin was now demonstrable in such calmodulin-depleted particulate preparations. Half-maximal stimulation of agonist-responsive adenylate cyclase occurred at 80 nM-calmodulin in the presence of 10 microM free Ca2+. Maximal stimulation by calmodulin (at 300-600 nM) restored enzyme activity to 89 +/- 5% (mean +/- S.E.M., n = 7) of the activity in untreated, calmodulin-intact, preparations. 相似文献
56.
Septal deviation is often associated with hypertrophy of the contralateral inferior turbinate. Failure to reduce the size of the turbinate at the time of septal reconstruction may result in persistent nasal obstruction. The authors present their experience with 408 patients who underwent one of four turbinate procedures over a 6-year period. Most patients underwent unilateral turbinate surgery, although bilateral procedures were undertaken in 7 percent of patients. A graduated surgical approach was taken that varied according to the amount of turbinate enlargement and the degree to which mucosa and bone were involved. Full-thickness excision of the anterior third to half of the inferior turbinate (turbinectomy) became a favored procedure. Relief of nasal obstruction was obtained in greater than 90 percent of patients. Healing was satisfactory regardless of the method, and complications, including hemorrhage and infection, were few. Long-term follow-up revealed no untoward sequelae, and no patient developed atrophic rhinitis. The authors conclude that turbinate surgery, particularly when unilateral, in the carefully selected patient with nasal obstruction is a useful adjunct to septal surgery. 相似文献
57.
Since 1974 a psychiatric hospital security unit, designed to serve the whole catchment area, has cared for mentally ill (mostly psychotic) patients with disturbed behaviour that cannot be managed in open wards. There are a few long-term dangerous patients but most stay only briefly. The admission of women to the unit was not followed by the expected reduction in violence. The unit has facilities for occupational therapy, physical recreation, work, and study, which are particularly important for those who are too dangerous to leave it. The unit''s calming influence depends as much on the supportive effect of the high staff ratio as on the use of tranquillisers. This type of unit is not suitable for patients with personality disturbances who "act out" or for mentally abnormal offenders; but it functions well as a crisis centre for the disturbed mentally ill, and there is an increasing demand for its services. 相似文献
58.
Abstract— The tetrahydrofolate-dependent serine hydroxymethyl transferase ( l -serine: tetrahydrofolate 10-hydroxymethyl transferase, EC 2.1.2.1) reaction in rat or human brain homogenates incubated aerobically is dependent on added reducing agents for full activity in order to protect the readily oxidized substrate, tetrahydrofolate. In this role, 0.1 m m -NADH is as affective as 10m m -2-mercaptoethanol and it can be shown that the NADH prevents destruction of tetrahydrofolate incubated with brain homogenates. If the dihydropteridine reductase (NADPH:6,7-dihydropteridine oxidoreductase, EC 1.6.99.7) activity of the brain homogenate is inhibited by a specific antiserum, NADH, but not 2-mercaptoeth-anol, is no longer effective. Furthermore, an homogenate of a brain biopsy from a human lacking dihydropteridine reductase requires added dihydropteridine reductase for maximal stimulation by NADH of the serine hydroxymethyl transferase reaction. We conclude that dihydropteridine reductase mediates the NADH stimulation and can play a role in preserving tetrahydrofolate from oxidation. The rinding of greatly reduced folate levels in the brain biopsy from the human lacking dihydropteridine reductase supports this postulated role of dihydropteridine reductase in folate metabolism. 相似文献
59.
G.W. Kidder Virginia C. Dewey Linda L. Nolan 《Archives of biochemistry and biophysics》1977,183(1):7-12
Adenine deaminase (adenine aminohydrolase, EC 3.5.4.2) has been found to occur in Crithidia fasciculata with a specific activity higher than that of the same enzymes of bacteria and yeasts. It is remarkable for its stability to heat, exhibiting no appreciable loss of activity after 60 min at 55 °C. It occurs in the soluble portion of cell extracts but can be released into the suspending medium by osmotic and/or cold shock. 相似文献
60.
The effects of dilauroylphosphatidylcholine (PC12) on ram epididymal sperm motility, acrosome reaction (AR) induction, plasma membrane permeability, mitochondrial function, and sperm penetration into zona-free hamster eggs were determined. PC12 (50 microM) induced cell motility in caput and cauda sperm, as measured by subjective estimation and automated motility analysis. Motion parameters of treated caput sperm approached those of control ejaculated sperm. Flow cytometric analysis revealed that membrane permeability to propidium iodide and mitochondrial uptake of rhodamine 123 changed during epididymal transit. PC12 induced the AR in sperm from all epididymal regions relative to control incubated sperm (caput 17% vs. control 8%; corpus 29% vs. control 13%; proximal cauda 48% vs. control 4%; distal cauda 51% vs. control 9%). After PC12 treatment, egg penetration by sperm was increased for sperm from the corpus (corpus 7% vs. control 0%) and cauda (proximal 48% vs. control 0%; distal 51% vs. control 0%), but not for caput sperm (caput 0% vs. control 0%). These studies establish that some sperm in each region of the epididymis possess the capacity for movement and the AR. Caput sperm, however, were unique in that they could not penetrate eggs. Additional maturational changes must occur in the caput and/or corpus epididymidis before penetration capacity can be expressed. 相似文献