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101.
The Escherichia coli somatic pilus, 987P, has been purified after removal by homogenization from a 987P+ enterotoxigenic E. coli. Cell-free pili were precipitated by the addition of MgCl2, collected, and dissolved in MgCl2-free buffer. Five cycles of precipitation and dissolving resulted in a preparation of 987P that was judged to be homogeneous based on electron microscopy and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the electron microscope, 987P was rod shaped, having a diameter of 7 nm and an apparent axial hole. Cells and membrane vesicles were not observed in the purified pilus preparation. Electrophoresis of 987P through sodium dodecyl sulfate-polyacrylamide gels resulted in a single band when the sample was denatured in the absence of mercaptoethanol and in two bands when the sample was denatured in the presence of mercaptoethanol. The calculated molecular weight of 987 was variable, depending upon the polyacrylamide concentration and whether mercaptoethanol was included in the denaturing solution. Chemically, 987P is composed primarily of protein but also contains an unidentified amino sugar. The amino terminal amino acid of 987P is alanine and its isoelectric point is pH 3.7. 987P possesses no detectable hemagglutinating activity. 相似文献
102.
Hydroperoxide-induced loss of pyridine nucleotides and release of calcium from rat liver mitochondria 总被引:11,自引:0,他引:11
H R L?tscher K H Winterhalter E Carafoli C Richter 《The Journal of biological chemistry》1980,255(19):9325-9330
It has been previously reported (L?tscher, H. R., Winterhalter, K. H., Carafoli, E., and Richter, C. (1979) Proc. Natl. Acad. Sci. U. S. A. 76, 4340-4344) that in Ca2+-loaded mitochondria hydroperoxides induce a release of Ca2+ from mitochondria and an irreversible oxidation of mitochondrial pyridine nucleotides. Here we show that in the presence of Ca2+ oxidized mitochondrial pyridine nucleotides are hydrolyzed inside mitochondria and that nicotinamide is released from mitochondria. The extent of the hydrolysis of NAD(P)+ is dependent on the amount of both hydroperoxide and Ca2+. The hydrolysis is reversible in the presence of added nicotinamide. The release of Ca2+ from mitochondria is electroneutral, and is directly or indirectly dependent on oxidized mitochondrial pyridine nucleotides. By contrast, the uptake of Ca2+ most probably does not require the present of reduced pyridine nucleotides. Control experiments show that even under the most drastic conditions employed in this study (100 nmol of Ca2+ and 85 nmol of t-butylhydroperoxide/mg of protein) mitochondria retain a considerable degree of functional integrity. 相似文献
103.
Replication of simian virus 40 chromatin in vitro depends on the amount of DNA polymerase alpha associated with replicating chromatin 总被引:7,自引:0,他引:7
Replication of simian virus 40 (SV40) chromatin in vitro is inhibited by chloride but stimulated by acetate anions even at physiological concentrations of 100-200 mM. In a similar fashion DNA polymerase alpha is affected with respect to the activity with activated DNA as primer template. Furthermore, at concentrations of 100-200 mM acetate DNA polymerase alpha remains associated with replicating chromatin, whereas association is strongly reduced when chloride anions are used at the corresponding concentrations. Thus the salt behaviour of DNA polymerase alpha explains the salt sensitivity of the replication system. Our results confirm the importance of this enzyme for DNA replication. 相似文献
104.
4-(3-Bromoacetylpyridinio)butyldiphosphoadenosine was synthesized with a [carbonyl-14C]acetyl label. The reactive coenzyme analogue inactivates alcohol dehydrogenase from Bacillus stearothermophilus by forming a covalent enzyme-coenzyme compound. The inactivation kinetics as well as the spectral properties of the modified enzyme after treatment with sodium hyposulphite suggest that the analogue is bound at the coenzyme binding site. B. stearothermophilus alcohol dehydrogenase modified with 14C-labelled coenzyme analogue and subseqeuntly carboxymethylated with unlabelled iodoacetic acid was digested with trypsin. The radioactive peptide was isolated and sequenced in parallel with the corresponding peptide similarly isolated from unmodified enzyme that had instead been carboxymethylated with iodo[14C]acetic acid. Amino acid and sequence analysis show that Cys-38 of the B. stearothermophilus alcohol dehydrogenase was modified by the reactive coenzyme analogue. This residue is homologous to Cys-43 in yeast alcohol dehydrogenase and Cys-46 in the horse liver enzyme but, unlike the latter two, Cys-38 is not reactive towards iodoacetate in the native bacterial enzyme. 相似文献
105.
106.
Infection of the temperature-sensitive E. coli CRT 266 (dnaBts) with T3-phages at the temperature of 30 degrees C and 35 degrees C, respectively, induced T3-specific RNA synthesis with a maximum rate at 7 min (30 degrees C) and 4.5 min (35 degrees C) after infection. At temperatures above 40 degrees C no T3-induced RNA synthesis could be observed. Infection of E. coli CR 34--45 (dnaB+) with T3 phages at 30 degrees C, 35 degrees C and at temperatures above 40 degrees C, however, produced T3-specific RNA synthesis. The maximum of T3-induced RNA synthesis could be observed between 7 min and 3 min depending on the temperature during infection. The inability to form T3-specific RNA after infection of E. coli CRT 266 at nonpermissive temperatures may be a cause for the absence of the formation of T3 phages and lysis of the host cells. 相似文献
107.
Amino acid sequence of the N-terminal non-collagenous segment of dermatosparactic sheep procollagen type I. 总被引:1,自引:0,他引:1
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H Rohde E Wachter W J Richter P Bruckner O Helles R Timpl 《The Biochemical journal》1979,179(3):631-642
The non-collagenous N-terminal segment of type I procollagen from dermatosparactic sheep skin was isolated in the form of the peptide Col 1 from a collagenase digest of the protein. The peptide has a blocked N-terminus, which was identified as pyrrolid-2-one-5-carboxylic acid. Appropriate overlapping fragments were prepared from reduced and alkylated peptide Col 1 by cleavage with trypsin at lysine, arginine and S-aminoethyl-cysteine residues and by cleavage with staphylococcal proteinase at glutamate residues. Amino acid sequence analysis of these fragments by Edman degradation and mass spectrometry established the whole sequence of peptide Col 1 except for a peptide junction (7--8) and a single Asx residue (44), and demonstrated that peptide Col 1 consists of 98 amino acid residues. The N-terminal portion of peptide Col 1 (86 residues) shows an irregular distribution of glycine, whereas the C-terminal portion (12 residues) possesses the triplet structure Gly-Xy and is apparently derived from the precursor-specific collagenous domain of procollagen. The central region of the peptide contains ten cysteine residues located between positions 18 and 73 and shows alternating polar and hydrophobic sequence elements. The regions adjacent to the cysteine-rich portion have a hydrophilic nature and are abundant in glutamic acid. The data are consistent with previous physicochemical and immunological evidence that distinct regions at the N- and C-termini of the non-collagenous domain possess a less rigid conformation than does the central portion of the molecule. 相似文献
108.
Representation of genomic kinetic sequence classes and sequence complexities were investigated in nuclear and polysomal RNA of the higher plant Petroselinum sativum (parsley). Two different methods indicated that most if not all polysomal poly(A) -RNA is transcribed from unique sequences. As measured by saturation hybridization in root callus and young leaves 8.7% and 6.2%, respectively, of unique DNA were transcribed in mRNA corresponding to 13.700 and 10.000 average sized genes. Unique nuclear DNA hybridized with an excess of polysomal poly(A)mRNA to the same extent as with total polysomal RNA. 3H-cDNA - poly(A)mRNA hybridization kinetics revealed the presence of two abundance classes with 9.200 and about 30 different mRNAs in leaves and two abundance classes with 10.500 and 960 different mRNAs in callus cells. The existence of plant poly(A)hnRNA was proven both by its fast kinetics of appearance, its length distribution larger than mRNA, and its sequence complexity a few times that of polysomal RNA. 相似文献
109.
1-Hexadecylpropanediol-3-phosphorylcholine, an ether-deoxy analog of lysophosphatidylcholine, has been employed to study the sensitivity of various types of mouse cells with respect to changes in membrane permeability induced by lysophosphatidylcholine. Cells used included erythrocytes, thymocytes, spleen cells and macrophage, as well as 4 different tumors (2 lymphomas, 1 Ehrlich acites and 1 methylcholanthren-induced fibrosarcoma). The sensitivity to the lysophosphatide (on a per-cell basis) of the above cell types varied by a factor of 65. When lytic concentrations were related to available membrane surface, this variation was reduced to a factor of 2.5. No principal difference was observed between the sensitivity of normal versus tumor cell membranes with respect to lysophosphatidylcholine lysis. Membrane surface, available for lysophosphatidylcholine, has been estimated from binding equilibria of 14C-labelled deoxy-lysophosphatidylcholine to the cells under standardized conditions. This method is based on the finding that binding equilibria of lysophospholipids to cells are predominantly determined by the available membrane surface. 相似文献
110.
Ultrastructure of Porocephalus crotali (Pentastomida) cuticle with phylogenetic implications. 总被引:1,自引:0,他引:1
The cuticle of P. crotali is pro-arthropodan, composed of an epi-, exo-, and endocuticle. The exo- and endocuticles are separated by a 600-A intermediate cuticular zone. The epicuticle is homogeneous and varies from 100 to 350 A in thickness. The exocuticle varies from 2 to eight mu in thickness and is divided into superficial and deep exocuticular zones. The endocuticle is lamellate and varies from 8 to 30 mu in thickness. Lamellae result from ordered parabolic orientations of 40-A chitin fibrils. Underlying cells lack a basement membrane. Subcuticular muscle cells insert tonofibrils directly into the adjacent endocuticle. No apodemes or apophyses occur. 相似文献