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1.
Monoclonal antibodies have been generated against a cross-link-containing derivative of alpha polymer (alpha XLCNBr), isolated following CNBr digestion of fibrin [Sobel, J. H., Ehrlich, P. H., Birken, S., Saffran, A. J., & Canfield, R. E. (1983) Biochemistry (preceding paper in this issue)]. One cloned cell line (F-102) was chosen for characterization based on its apparent specificity for the A alpha-chain region A alpha 518-584 (CNBr X). A second line (F-103) was selected because of its anti-A alpha 241-476 (CNBr VIII) properties. These two regions of the A alpha chain have previously been implicated as major contributors to the cross-linking process that leads to alpha-polymer formation. Radioimmunoassays have been developed, employing the immunoglobulins produced by clones F-102 and F-103. These assays have been applied, in conjunction with high-performance liquid chromatography purified tryptic and chymotryptic derivatives of CNBr VIII and CNBr X, to localize the respective determinants involved in antibody binding. In each case, virtually full immunoreactivity was exhibited by both the CNBr fragment and a single tryptic or chymotryptic peptide originating from it. These findings indicate that sequence-specific, rather than conformational, determinants were operative in the generation of antibodies F-102 and F-103. The epitope recognized by F-102 was localized to the region of A alpha 540-554, while the F-103 binding site resided within A alpha 259-276. When these radioimmunoassays were applied to study the relative immunoreactivity exhibited by a variety of fibrinogen derivatives, the results obtained support earlier suggestions that the COOH-terminal portion of the A alpha chain contains regions of random conformation. 相似文献
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3.
We have developed a procedure for Vibratome (Oxford Laboratories) sections that is particularly valuable for providing uniformly thick, well preserved CNS tissue sections for morphometric applications. 相似文献
4.
The substrate analogue 3-bromo-2-ketoglutarate reacts with pig heart NADP+-dependent isocitrate dehydrogenase to yield partially inactive enzyme. Following 65% inactivation, no further inactivation was observed. Concomitant with this inactivation, incorporation of 1 mol of reagent/mol of enzyme dimer was measured. The dependence of the inactivation rate on bromoketoglutarate concentration is consistent with reversible binding of reagent (KI = 360 microM) prior to irreversible reaction. Manganous isocitrate reduces the rate of inactivation by 80% but does not provide complete protection even at saturating concentrations. Complete protection is obtained with NADP+ or the NADP+-alpha-ketoglutarate adduct. By modification with [14C]bromoketoglutarate or by NaB3H4 reduction of modified enzyme, a single major radiolabeled tryptic peptide was obtained by high performance liquid chromatography with the sequence: Asp-Leu-Ala-Gly-X-Ile-His-Gly-Leu-Ser-Asn-Val-Lys. Evidence in the following paper (Bailey, J.M., Colman, R.F. (1987) J. Biol. Chem. 262, 12620-12626) indicates that X is glutamic acid. Enzyme modified at the coenzyme site by 2-(bromo-2,3-dioxobutylthio)-1,N(6)-ethenoadenosine 2',5'-biphosphate in the presence of manganous isocitrate is not further inactivated by bromoketoglutarate. Bromoketoglutarate-modified enzyme exhibits a stoichiometry of binding isocitrate and NADPH equal to 1 mol/mol of enzyme dimer, half that of native enzyme. These results indicate that bromoketoglutarate modifies a residue in the nicotinamide region of the coenzyme site proximal to the substrate site and that reaction at one catalytic site of the enzyme dimer decreases the activity of the other site. 相似文献
5.
Mella Adlersberg Kuo-Peing Liu Shu-Chi Hsiung Yigal Ehrlich Hadassah Tamir 《Journal of neurochemistry》1987,49(4):1105-1115
The endogenous phosphorylation of serotonin binding protein (SBP), a soluble protein found in central and peripheral serotonergic neurons, inhibits the binding of 5-hydroxytryptamine (5-HT, serotonin). A protein kinase activity that copurifies with SBP (SBP-kinase) was partially characterized and compared with calcium/calmodulin-dependent protein kinase II (CAM-PK II). SBP itself is not the enzyme since heating destroyed the protein kinase activity without affecting the capacity of the protein to bind [3H]5-HT. SBP-kinase and CAM-PK II kinase shared the following characteristics: (1) size of the subunits; (2) autophosphorylation in a Ca2+-dependent manner; and (3) affinity for Ca2+. In addition, both forms of protein kinase phosphorylated microtubule-associated proteins well and did not phosphorylate myosin, phosphorylase b, and casein. Phorbol esters or diacylglycerol had no effect on either of the protein kinases. However, substantial differences between SBP-kinase and CAM-PK II were observed: (1) CAM enhanced CAM-PK II activity, but had no effect on SBP-kinase; (2) synapsin I was an excellent substrate for CAM-PK II, but not for SBP-kinase; (3) 5-HT inhibited both the autophosphorylation of SBP-kinase and the phosphorylation of SBP, but had no effect on CAM-PK II. These data indicate that SBP-kinase is different from CAM-PK II. Phosphopeptide maps of SBP and SBP-kinase generated by digestion with S. aureus V8 protease are consistent with the conclusion that these proteins are distinct molecular entities. It is suggested that phosphorylation of SBP may regulate the transport of 5-HT within neurons. 相似文献
6.
Effect on aflatoxin production of competition between wild-type and mutant strains of Aspergillus parasiticus 总被引:4,自引:0,他引:4
K. Ehrlich 《Mycopathologia》1987,97(2):93-96
Co-cultivation of a strain of Aspergillus parasiticus, capable of making aflatoxins, with blocked mutant strains, capable of producing none or only a low level of aflatoxins, reduced the net yield of aflatoxins more than that expected based on spore recovery. Yields of aflatoxins were 8-fold less for a norsolorinic acid-producing strain, 14-fold less for an averantin-producing strain, 6-fold less for an averufin-producing strain, and 21-fold less for a versicolorin A-producing strain when co-cultured in equal amounts with a wild-type strain of Aspergillus parasiticus. Even when the wild-type strain was initially present in 100-fold excess, with two of the mutant strains, reduced aflatoxin production was still observed. 相似文献
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8.
A system allowing the induction of DNA amplification in Bacillus subtilis was developed, based on a thermosensitive plasmid, pE194, stably integrated in the bacterial chromosome. An amplification unit, comprising an antibiotic resistance marker flanked by directly repeated sequences, was placed next to the integrated plasmid. Activation of pE194 replication led to DNA amplification. Two different amplification processes appeared to take place: one increased the copy number of all sequences in the vicinity of the integrated plasmid and was possibly of the onion skin type, while the other increased the copy number of the amplification unit only and generated long arrays of amplification units. These arrays were purified and shown to consist mainly of directly repeated amplification units but to also contain non-linear regions, such as replication forks and recombination intermediates. They were attached to the chromosome at one end only, and were, in general, not stably inherited, which suggests that they are early amplification intermediates. Longer arrays were detected before the shorter ones during amplification. When the parental amplification unit contained repeats which differed by a restriction site the arrays which derived thereof contained in a majority of cases only a single type of repeat. We propose that the amplified DNA is generated by rolling circle replication, and that such a process might underlie a number of amplification events. 相似文献
9.
To establish the chromosomal location of the human ACHE gene encoding the acetylcholine hydrolyzing enzyme acetylcholinesterase (ACHE, acetylcholine acetylhydrolase, E.C. 3.1.1.7), a human-specific polymerase chain reaction (PCR) procedure that supports the selective amplification of ACHE DNA fragments from human genomic DNA was employed with 19 human-hamster somatic cell hybrids carrying one or more human chromosomes. Informative ACHE-specific PCR fragments were produced from two cell lines, both of which include human chromosome 7, but not with DNA from 17 cell hybrids carrying various combinations of all human chromosomes other than 7. Fluorescent in situ hybridization of biotinylated ACHE DNA with metaphase chromosomes from human peripheral blood lymphocytes revealed prominent labeling on the 7q22 position. Therefore, further tests were performed to confirm the chromosome 7 location. DNA samples from the two cell lines including chromosome 7 and the ACHE gene were positive with PCR primers informative for the human cystic fibrosis CFTR gene, known to reside at the 7q31.1 position, but negative for the ACHE-related butyrylcholinesterase (BCHE, acylcholine acylhydrolase, E.C. 3.1.1.8) gene, mapped at the 3q26-ter position, confirming that these lines contain chromosome 7 but not chromosome 3. In contrast, three other cell lines including chromosome 3, but not 7, were BCHE-positive and ACHE-negative. In addition, genomic DNA from a sorted chromosome 7 library supported the production of ACHE- but not BCHE-specific PCR products, whereas with DNA from a sorted chromosome 3 library, the BCHE but not the ACHE fragment was amplified.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
10.
The replication termination signal terB of the Escherichia coli chromosome is a deletion hot spot. 总被引:9,自引:3,他引:6 下载免费PDF全文
Hybrids composed of phage M13, plasmid pBR322 and the termination signal of Escherichia coli chromosome replication terB were used to show that arrest of DNA synthesis creates a very efficient deletion hot spot. Up to 80% of deletions occurring in these hybrids had one deletion end-point at terB provided that (i) terB was oriented to arrest M13 and pBR322 leading strand synthesis; and (ii) the host cells contained the Tus protein necessary for arresting DNA synthesis at terB. The position of terB and the flanking sequences had little effect on deletion hot spot activity. About 90% of the deletions at terB ended 5-6 nucleotides in front of the major replication arrest site. We propose two models to account for deletion formation and speculate that many genome rearrangements may be due to the pausing of DNA replication. 相似文献