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111.
Neuropeptide Y (NPY) has been isolated and sequenced from brain extracts of the European common frog, Rana temporaria. Plasma desorption mass spectroscopy of the purified peptide indicated a molecular mass of 4243.3 Da which was in agreement with that deduced from the sequence (4243.7 Da), incorporating a C-terminal amide. The primary structure of frog NPY was established as: YPSKPDNPGEDAPAEDMAKYYSALRHYINLITRQRY-NH2. Frog NPY contains a single, highly-conservative amino acid substitution (Lys for Arg at residue 19) with respect to human NPY. NPY immunoreactivity was localised exclusively in nerves within the brain, pancreas and gastrointestinal tract and reverse-phase HPLC of extracts of these tissues resolved a single immunoreactive peptide of identical retention time in each case. The primary structure of NPY has therefore been highly-conserved over a considerable evolutionary time-span. 相似文献
112.
Plant thioredoxin h: an animal-like thioredoxin occurring in multiple cell compartments 总被引:8,自引:0,他引:8
F Marcus S H Chamberlain C Chu F R Masiarz S Shin B C Yee B B Buchanan 《Archives of biochemistry and biophysics》1991,287(1):195-198
Thioredoxin h has been purified to electrophoretic homogeneity from spinach roots using a procedure devised for leaves. The root thioredoxin (h2 form) differed from chloroplast and animal thioredoxins in showing an atypical active site (Cys-Ala-Pro-Cys) but otherwise resembled animal thioredoxin in structure. Sequence data for a total of 72 residues of spinach root thioredoxin h2 (about 69% of the primary structure) showed 43-44% identity with rabbit and rat thioredoxin. Analysis of cell fractions from the endosperm of germinating castor beans revealed that thioredoxin h occurs in the cytosol, endoplasmic reticulum, and mitochondria. The present findings demonstrate a similarity between plant thioredoxin h and animal thioredoxins in structure and intracellular location and raise the question of whether these proteins have similar functions. 相似文献
113.
The distribution of neuropeptides in the ocular tissues of several mammals: a comparative study. 总被引:3,自引:0,他引:3
A A Elbadri C Shaw C F Johnston D B Archer K D Buchanan 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1991,100(3):625-627
1. The distribution of several neuropeptides (vasoactive intestinal peptide, substance P, somatostatin and neurotensin) was assessed in ocular tissues from the cow, sheep, rabbit and rat. 2. Vasoactive intestinal peptide was most abundant in the choroid and sclera in all species except the rat. Substance P was most abundant in the retina of cow and rat and in the iris/ciliary body of sheep and rabbit. Somatostatin and neurotensin were most abundant in the retina of all species examined. 3. Regulatory peptides thus display distinct regional distributions within the ocular tissues of a single species of mammal and, in addition, exhibit interspecific variation. 相似文献
114.
115.
Phosphorylation of CTP:phosphocholine cytidylyltransferase in vivo. Lack of effect of phorbol ester treatment in HeLa cells 总被引:1,自引:0,他引:1
The production and characterization of an antibody to rat liver CTP:phosphocholine cytidylyltransferase is described. This antibody quantitatively precipitated cytidylyltransferase from both rat liver and HeLa cell cytosol. Following affinity purification, the antibody was used to demonstrate, for the first time, the phosphorylation of cytidylyltransferase in vivo. Following the immunoprecipitation of cytidylyltransferase from HeLa cells, acid hydrolysis, and thin layer electrophoresis of the amino acids, only [32P]phosphoserine was detected. The phosphorylation state of cytidylyltransferase in HeLa cells was examined following treatment with phorbol ester for 1 h. In agreement with previous studies, the incorporation of [3H]choline into phosphatidylcholine via the CDP-choline pathway was stimulated 5-fold in cultures of HeLa cells following treatment with phorbol ester for 1 h. However, no appreciable translocation of cytidylyltransferase was detected, despite the utilization of two different methods of cell lysis. Furthermore, the inclusion of phosphatase inhibitors and chelators of divalent cations in the homogenization buffers had no effect on the observed distribution or activity of the enzyme. Immunoprecipitated cytidylyltransferase was phosphorylated to the same extent, and on serine residues only, in both control and 12-O-tetradecanoyl phorbol-13-acetate (TPA)-treated cells. Measurement of the pool sizes of the aqueous intermediates of the CDP-choline pathway, following TPA treatment, revealed a modest decrease in the phosphocholine pool only, consistent with an activation of cytidylyltransferase. 相似文献
116.
Two polyclonal antibodies were raised to synthetic peptides corresponding to amino acids Ser21-Tyr35 and Lys247-Phe261 of cytochrome b561. These antibodies were used to test the native orientation of the amino and carboxyl termini of this transmembrane electron transport protein. Carboxyl-terminal epitopes were lost when intact chromaffin granules were treated with Pronase. This result indicates that the carboxyl terminus is cytoplasmically exposed and confirms a theoretical prediction obtained from hydropathy plots. Epitopes that were recognized by an amino-terminal antipeptide antibody were not removed under the same conditions. This finding implied that the amino terminus was not proteolytically accessible on the exterior of the granule. The abundance of threonine and serine residues in the amino-terminal region suggested that the amino terminus could be held in the membrane by covalent fatty acylation. Treatment of purified delipidated cytochrome b561 with hydroxylamine resulted in the release of a fatty acid hydroxamate. Sulfhydryl analysis of purified cytochrome b561 showed that all 3 cysteine residues were in the free sulfhydryl form. These observations indicate that cytochrome b561 is covalently fatty acylated and that the lipid is bound through ester linkages of serine or threonine residues. 相似文献
117.
118.
A. Henry Latorella Susan K. Bromberg Kent Lieber James Robinson 《Journal of phycology》1981,17(2):211-214
Fifteen nitrate assimilation-deficient mutants of the euryhaline green alga, Dunaliella tertiolecta Butcher were selected by their chlorate resistance. Ten mutants, unable to grow on NO3? but able to grow on NO2?, had no detectable nitrate reductase activity. Five mutants, unable to grow on either NO3? or NO2?, had depressed levels of both nitrate and nitrite reductase. A method for assaying methyl viologen-nitrate reductase in the presence of nitrite reductase is described. 相似文献
119.
Properties of the Photosynthetic System and DNA of Cyanophora paradoxa Cyanelles 总被引:1,自引:1,他引:0 下载免费PDF全文
The cyanelle from the photosynthetic biflagellate protist Cyanophora paradoxa has been studied in terms of its photosynthetic properties. Structurally, the cyanelle resembles unicellular cyanobacteria. The cyanelle is readily released from the host cell by means of the French press. The isolated cyanelle shows typical photosystem I and photosystem II activities as well as phenazine methosulfate-mediated photophosphorylation. The kinetic parameters Km and Vmax were determined for CO2 fixation in the cyanelle and cells of C. paradoxa and compared to a cyanobacterium. The determined values were not much different, although the cyanobacterium had a significantly greater rate of CO2 fixation, and the cyanelle was least active in this regard. Photosystem I chlorophyll-protein complex is readily isolated from the thylakoid membrane. In all these respects, the photosynthetic apparatus of the cyanelle resembles that of cyanobacteria. No nitrogen fixation activity was observed. Attempts to regenerate the isolated cyanelle were not successful, but in some cases, an unidentified cyanobacterium grew up in standing cultures of C. paradoxa cyanelles. Buoyant density data indicate that the strain of C. paradoxa we have investigated differs from that employed by others, since our strain shows a value of 1.716 grams per cubic centimeter and others report values of 1.695 and 1.691. 相似文献
120.
Simultaneous kinetic analysis of ribulose 1,5-bisphosphate carboxylase/oxygenase activities 总被引:4,自引:4,他引:0 下载免费PDF全文
An assay was developed for simultaneous kinetic analysis of the activities of the bifunctional plant enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase [EC 4.1.1.39]. [1-14C,5-3H]Ribulose 1,5-bisphosphate (RuBP) was used as the labeled substrate. Tritium enrichment of the doubly labeled 3-phosphoglycerate (3-PGA) product, common to both enzyme activities, may be used to calculate Vc/Vo ratios from the expression A/(B-A) where A and B represent the 3H/14C isotope ratios of doubly labeled RuBP and 3-PGA, and Vc and Vo represent the activities of carboxylase and oxygenase, respectively. Doubly labeled substrate was synthesized from [2-14C]glucose and [6-3H]glucose using the enzymes of the pentose phosphate pathway coupled with phosphoribulokinase. 相似文献