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Wegener, Warner S. (Albert Einstein Medical Center, Philadelphia, Pa.), Henry C. Reeves, and Samuel J. Ajl. Heterogeneity of the glyoxylate-condensing enzymes. J. Bacteriol. 90:594-598. 1965.-Evidence is presented that the enzymatic condensations of glyoxylate with acetyl-CoA (malate synthase), propionyl-CoA (alpha-hydroxyglutarate synthase), butyryl-CoA (beta-ethylmalate synthase), and valeryl-CoA (beta-n-propylmalate synthase) are catalyzed by different enzymes. The possibility that these activities resulted from a single enzyme possessing a broad fatty acid acyl-CoA substrate specificity was ruled out. The latter was suggested by the fact that cells grown on a number of short-chain fatty acids exhibited all the above activities. The conclusion that these reactions are catalyzed by different enzymes is based on the following considerations: (i) the enzymes can be differentially inactivated by heat; (ii) under various growth conditions, where all the condensing enzymes are present, their respective activities do not show a constant ratio, as would be expected if they were catalyzed by a single enzyme; and (iii) under appropriate growth conditions, one or more of these enzymes has been shown to be present to the exclusion of others. 相似文献
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Procedures for the Generation of Mature Chlamydomonas reinhardtii Zygotes for Molecular and Biochemical Analyses
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Zygotes represent an important stage in the sexual cycle of the unicellular green alga Chlamydomonas reinhardtii. To study zygote germination at a molecular level, a protocol was elaborated for the generation of zygotes in large quantities and a method was developed for the extraction from zygotes of RNA that could be translated in vitro. 相似文献
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Thomas F. Holzman Christine C. Chung Rohinton Edalji David A. Egan Earl J. Gubbins Annemarie Rueter Gail Howard Lana K. Yang Terry M. Pederson Grant A. Krafft et al. 《Journal of Protein Chemistry》1990,9(6):663-672
The gene for human preprorenin was obtained from total RNA prepared from primary human chorion cells. An expression vector was constructed containing an SV40 early promoter, a human preprorenin cDNA, bovine growth hormone poly-A addition signal, and a dihydrofolate reductase (dhfr) expression cassette. This vector was inserted into the DXB-11 Chinese hamster ovary (CHO) cell line. The recombinant protein was exported by CHO cells into the tissue culture media. At harvest the prorenin levels ranged from 1–5 mg/L. For prorenin isolation the cell culture supernatants were processed by filtration, concentration, dialysis, and batch extraction. Preparative-scale isolation of prorenin was accomplished using blue-dye chromatography and size-exclusion chromatography. The isolated prorenin yielded a single SDS-gel band with Mr 40,000. The proprotein was characterized with respect to N-terminal sequence and N-linked sugar composition. Trypsin-activated renin prepared from the proprotein was characterized with respect to N-terminal sequence andpH-activity profile. Enzyme activity was measured with a newly developed fluorogenic peptide substrate containing the P6-P3 sequence of human angiotensinogen. 相似文献
6.
The maturation of zygotes formed by the fusion of two gametes is the essential part of the diploid phase of the Chlamydomonas reinhardtii sexual life cycle and results in mature zygotes competent to germinate. To understand the molecular mechanisms underlying zygote maturation and the attainment of competence for germination we isolated genomic clones representing three different genes that are specifically expressed in Chlamydomonas reinhardtii zygotes. Accumulation of the RNAs started more than 24 h after mating, setting these genes apart from genes expressed in young zygotes [9]. Upon light-induced germination of zygotes, the mRNAs disappeared. The patterns of RNA accumulation and disappearance were gene-specific and suggested a function of these genes in maturation and/or in initial steps of germination. 相似文献
7.
Summary Thin sections of budding yeast cells and giant gells grown after X-irradiation have been examined by electron microscopy. The different steps of cross-wall formation during budding were documented with unirradiated cells. With X-ray induced giant cells cytokinesis was shown to be absent. Neither primary nor secondary septae appeared thus cell separation did not occur. Despite this fact both macromolecular synthesis and bud growth continued, giving rise to the formation of giant cells. 相似文献
8.
W A Wegener 《Biophysical journal》1984,46(6):795-803
Pump-and-probe techniques can be used to follow the slow rotational motions of fluorescent labels bound to macromolecules in solution. A strong pulse of polarized light initially anisotropically depletes the ground-state population. A continuous low-intensity beam of variable polarization then probes the anisotropic ground-state distribution. Using an additional emission polarizer, the generated fluorescence can be recorded as it rises towards its prepump value. A general theory of fluorescence recovery spectroscopy (FRS) is presented that allows for irreversible depletion processes like photobleaching as well as slowly reversible processes like triplet formation. In either case, rotational motions modulate recovery through cosine-squared laws for dipolar absorption and emission processes. Certain pump, probe, and emission polarization directions eliminate the directional dependence of either dipole and simplify the resulting expressions. Two anisotropy functions can then be constructed to independently monitor the rotations of either dipole. These functions are identical in form to the anisotropy used in fluorescence depolarization measurements and all rotational models developed there apply here with minor modifications. Several setups are discussed that achieve the necessary polarization alignments. These include right-angle detection equipment that is commonly available in laboratories using fluorescence methods. 相似文献
9.
Ronald Bontrop Marcel Tilanus Marlies Mikulski Marja van Eggermond Annemarie Termijtelen Marius Giphart 《Immunogenetics》1986,23(6):401-405
HLA-DR molecules were isolated from eight different HLA-DR3 homozygous B-cell lines by immunoprecipitation with monoclonal antibodies, and they were subsequently analyzed by two-dimensional gel electrophoresis. We found that HLA-DR3 homozygous B-cell lines of consanguineous origin express two types of HLA-DR molecules. One type of HLA-DR molecule was present in all the cell lines tested, whereas the second DR molecule appears to be polymorphic. DNA isolated from the different HLA-DR3 homozygous cell lines was studied by Southern blot analysis to determine whether any DR restriction fragment length polymorphism could be observed. Polymorphisms detected at both the product and genomic level have been compared to each other, and their relations to the serological (HLA-DR) and cellular (HLA-D and LB-Q1) typing data will be discussed.No reprints available 相似文献
10.
Annemarie Surlykke Matija Gogala 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1986,159(2):267-273
Summary MaleThecophora fovea (Tr.) (Noctuidae) sing continuously for several minutes by rubbing the 1. tarsal segment of the metathoracic leg against a stridulatory swelling on the hindwing. In Northern Yugoslavia (Slovenia) the males emerge in late October and start stridulating about a week later when the females emerge.The sounds are pulse trains consisting of 10–12 ms long sound pulses with main energy around 32 kHz and a PRR of 20 pulses/s. The mechanics of the sound producing apparatus was studied by activating the stridulatory swelling with short sound impulses. The impulse response of the swelling was recorded by laser vibrometry and amplitude spectra of the vibrations showed maximum velocities between 25 and 35 kHz. Hence, it seems likely that the stridulatory swelling is driven as a mechanical oscillator with a resonance frequency which determines the carrier frequency of the sounds.Audiograms of both males and females showed peak sensitivities at 25–30 kHz. The median threshold at the BF was 36 dB SPL. The peak intensity of the sound pulses was 83 dB SPL at 1 m, which should enable the moths to hear each other at distances of around 30 m. Therefore sound production inT. fovea might function in long distance calling. It is argued thatT. fovea can survive making such a noise in spite of being palatable to bats because it flies so late in the year that it is temporally isolated from bats.Abbreviations
PRR
pulse repetition rate
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SPL
sound pressure level
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BF
best frequency 相似文献