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101.
The incubation of peptidoglycan fragments with ether-treated cells of Neisseria gonorrhoeae resulted in breakdown products that showed the presence of previously undescribed lytic enzymes. The properties of an endopeptidase able to hydrolyse peptide-linked bis-disaccharide peptide dimer to monomer units were examined. An exo-N-acetyl-glucosaminidase was also shown to release free N-acetylglucosamine. The breakdown pattern of glycosidically-linked dimer indicated the existence of an endo-N-acetylglucosaminidase. The activities of the latter enzyme and of the endopeptidase were both sensitive to beta-lactam antibiotics. 相似文献
102.
Specificity of the Na+-dependent monocarboxylic acid transport pathway in rabbit renal brush border membranes 总被引:7,自引:0,他引:7
Edward P. Nord Stephen H. Wright Ian Kippen Ernest M. Wright 《The Journal of membrane biology》1983,72(3):213-221
The substrate specificity of a Na+-dependent transport pathway for L-lactate was studied in rabbit renal brush border membrane vesicles. Jmax for L-lactate transport was unaffected by the presence of a fixed concentration of two different short-chain monocarboxylic acids, while the apparent Kt(Ka) for L-lactate increased, and this is compatible with competitive inhibition. The inhibitor constants ("Ki"'s) for the transport pathway for the two solutes examined closely corresponded to the respective "Ki"'s derived from a Dixon plot. A broad range of compounds were then tested as potential inhibitors of L-lactate transport, and the "Ki"'s thereby derived yielded specific information regarding optimal substrate recognition by the carrier. A single carboxyl group is an absolute requirement for recognition, and preference is given to 3 to 6 C chain molecules. Addition of ketone, hydroxyl and, particularly, amine groups at any carbon position, diminishes substrate-carrier interaction. Intramolecular forces, notably the inductive effects of halogens, may play a role in enhancing substrate-carrier interaction; however, no correlation was found between pKa and "Ki" for the substrates examined. We conclude that a separate monocarboxylic acid transport pathway, discrete from either the D-glucose, alpha or beta neutral amino-acid, or dicarboxylic acid carriers, exists in the renal brush border, and this handles a broad range of monocarboxylates. 相似文献
103.
James W. Cosgrove John J. Heikkila Alexander Marks Ian R. Brown 《Journal of neurochemistry》1983,40(3):806-813
Abstract: Free and membrane-bound polysomes were isolated from the cerebral hemispheres and cerebellum of the young adult rabbit. The two polysomal populations were translated in an mRNA-dependent cell-free system derived from rabbit reticulocytes. Analysis of the [35 S]methionine-labeled translation products on two-dimensional polyacrylamide gels indicated an efficient separation of the two classes of brain polysomes. The relative synthesis of S100 protein by free and membrane- bound polysomes was determined by direct immuno-precipitation of the cell-free translation products in the presence of detergents to reduce nonspecific trapping. Synthesis of S100 protein was found to be twofold greater on membrane-bound polysomes compared with free polysomes isolated from either the cerebral hemispheres or the cerebellum. In addition, the proportion of poly- (A+)mRNA coding for SlOO protein was also twofold greater in membrane-bound polysomes compared with free polysomes isolated from the cerebral hemispheres. These results indicate that the cytoplasmic S100 protein is synthesized predominantly on membrane-bound polysomes in the rabbit brain. We suggest that the nascent S100 polypeptide chain translation complex is attached to the rough endoplasmic reticulum by an ionic interaction involving a sequence of 13 basic amino acids in S100 protein. 相似文献
104.
The H-2
dm1
mutation and Qa antigens 总被引:2,自引:0,他引:2
P. Mark Hogarth Ian D. Walker Aveline J. Rigby Ian F. C. McKenzie 《Immunogenetics》1983,18(6):617-624
The effect of the H-2dm1 mutation on Qa-m2 expression was examined. The mutant strain B10.D2-H-2dm1 showed a fourfold increase in Qa-m2 expression when compared with the parental strain B10.D2. Qa-m2 molecules immunoprecipitated from B10.D2-H-2dm1, C57BL/10, and B10.D2 spleen cells were identical by two-dimensional (2-D) gel electrophoresis [isoelectric focusing (IEF) followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE]). It is likely therefore that the increased Qa-m2 expression is not due to gross structural alterations of the Qa-m2 molecule; in the present study, alternative explanations are discussed. 相似文献
105.
R E Perkins S C Conroy B Dunbar L A Fothergill M F Tuite M J Dobson S M Kingsman A J Kingsman 《The Biochemical journal》1983,211(1):199-218
The complete amino acid sequence of yeast phosphoglycerate kinase, comprising 415 residues, was determined. The sequence of residues 1-173 was deduced mainly from nucleotide sequence analysis of a series of overlapping fragments derived from the relevant portion of a 2.95-kilobase endonuclease-HindIII-digest fragment containing the yeast phosphoglycerate kinase gene. The sequence of residues 174-415 was deduced mainly from amino acid sequence analysis of three CNBr-cleavage fragments, and from peptides derived from these fragments after digestion by a number of proteolytic enzymes. Cleavage at the two tryptophan residues with o-iodosobenzoic acid was also used to isolate fragments suitable for amino acid sequence analysis. Determination of the complete sequence now allows a detailed interpretation of the existing high-resolution X-ray-crystallographic structure. The sequence -Ile-Ile-Gly-Gly-Gly- occurs twice in distant parts of the linear sequence (residues 232-236 and 367-371). Both these regions contribute to the nucleoside phosphate-binding site. A comparison of the sequence of yeast phosphoglycerate kinase reported here with the sequences of phosphoglycerate kinase from horse muscle and human erythrocytes shows that the yeast enzyme is 64% identical with the mammalian enzymes. The yeast has strikingly fewer methionine, cysteine and tryptophan residues. 相似文献
106.
107.
Anders Fjose Ian F. Pryme Johan R. Lillehaug 《Molecular and cellular biochemistry》1983,56(2):137-144
Summary After transfer of Krebs II ascites cells from the mouse peritoneum to suspension culture addition of the phorbol ester 12-0-tetradecanoyl-phorbol-13-acetate (TPA) causes an early stimulation of 3H-choline incorporation into phosphatidylcholine (PC). Choline transport into the treated cells, however, was unaffected. Within 30 min of TPA treatment 3H-choline incorporation was almost 300% above the control level. During a 5 hr period of suspension culture the overall patterns of 3H-choline incorporation were similar in TPA-treated and control cultures though the rate was greatly accentuated by the presence of the phorbol ester. Incubation of cells with cycloheximide prior to incubation with TPA did not result in an inhibition of the TPA-directed 3H-choline incorporation. After 3 hr incubation with TPA there were large increases in radioactivity in all subcellular fractions. At 20 hr, however, the values were not far from those of the control. During the first 3 hr of incubation with TPA the incorporation of 3H-choline into light rough (LR) and smooth (S) membranes was stimulated to levels of 400% and 320% respectively above control values. At later times the profiles of radioactivity in membrane subfractions in TPA-treated and control cultures were similar. The results illustrate an early effect of TPA on PC biosynthesis in Krebs II ascites cells while at later times of incubation the stimulatory effect was virtually abolished. 相似文献
108.
109.
Alan Shiels Stephen Jeffery Ian R. Phillips Elizabeth A. Shephard Catherine A. Wilson Nicholas D. Carter 《Biochimica et Biophysica Acta (BBA)/General Subjects》1983,760(3)
Using radioimmunoassay, the concentration of carbonic anhydrase III in the livers of adult male rats was found to be approx. 30-times greater than that observed in mature females. Castration of male rats led to a marked reduction in liver carbonic anhydrase III concentrations which could be partially restored to control levels by testosterone replacement. Administration of testosterone to ovariectomised female rats induced about a 5-fold increase in liver carbonic anhydrase III concentration. Immunoprecipitation analysis of the products of liver mRNA translation in vitro with antiserum specific for carbonic anhydrase III showed that hormonal control of the levels of carbonic anhydrase III in liver is mediated by changes in the amount of translatable carbonic anhydrase III mRNA. Marked changes in liver carbonic anhydrase III concentrations were also observed in developing and ageing male rats. 相似文献
110.
There is some apprehension about the possible effect of the introduced American mink Mustela vison upon the indigenous British fauna, either as a predator exerting new and excessive pressure upon native prey species, or as a carnivore competing for prey resources against native carnivores. Concern is also felt by preservers of game, and by keepers of small domestic animals (poultry and rabbits) about the mink's potential as a pest. To investigate the food habits of the mink in England and Wales the alimentary canals of 1165 trapped animals were examined, yielding 204 samples for analysis. The resulting information provides a general picture of the mink's diet, including seasonal variations. Comparisons were possible with similar work carried out in other countries, and with the diets of other British carnivores. Tentative conclusions were reached regarding the broad pattern of food relationships between the mink and other British animals, wild and domestic. 相似文献