Rat hepatic uroporphyrinogen III co-synthase. Purification and evidence for a bound folate coenzyme participating in the biosynthesis of uroporphyrinogen III.

Rat hepatic uroporphyrinogen III co-synthase was isolated and purified 73-fold with a 13% yield by (NH4)2SO4 fractionation and sequential chromatography on DEAE-Sephacel, Sephadex G-100 (superfine grade) and folate-AH-Sepharose 4B. The purified co-synthase has an Mr of approx. 42 000, and is resolved into two bands, each possessing co-synthase activity, by polyacrylamide-gel electrophoresis. A factor was dissociated from the purified co-synthase. Results of both microbiological and competitive protein-binding assays suggest that it is a pteroylpolyglutamate. The isolated pteroylpolyglutamate factor was co-eluted with authentic N5-methyltetrahydropteroylheptaglutamate on DEAE-Sephacel. Uroporphyrinogen III is formed by cosynthase-free preparations of uroporphyrinogen I synthase in the presence of tetrahydropteroylglutamate. Tetrahydropeteroylheptaglutamate is also able to direct the formation of equivalent amounts of uroporphyrinogen III at a concentration approximately one-hundredth that of tetrahydropteroylmonoglutamate. These results suggest that a reduced pteroylpolyglutamate factor is associated with rat hepatic uroporphyrinogen III co-synthase, and that this may function as a coenzyme for the biosynthesis of uroporphyrinogen III.     

The IgM-associated protein mb-1 as a marker of normal and neoplastic B cells.

Recent evidence indicates that the transmembrane form of IgM on murine and human B lymphocytes is physically associated with at least two proteins, forming a disulfide-linked dimer, which may control cell surface expression of IgM and also play a role in signal transduction after Ag binding (by analogy with the TCR-associated CD3 components in T lymphocytes). We have used mAb and polyclonal antibodies against an intracytoplasmic epitope on one of these polypeptides (previously identified in murine B cells as the product of the B cell specific mb-1 gene) to study the distribution of the IgM-associated dimer in human cells. By immunocytochemical staining of normal and neoplastic B cells, we show that the human mb-1 protein appears early in B cell differentiation, probably before expression of cytoplasmic mu-chain, and persists until the plasma cell stage, where it is seen as an intracytoplasmic component. According to immunohistologic analysis of reactive lymphoid tissue and lymphoma samples, mb-1 protein is completely B cell specific. Anti-mb-1 also labels B cell areas in tissues from seven different mammalian species. Finally, the Ig-associated dimer could be isolated from human hairy-cell leukemia cells in high purity and yield by affinity chromatography using anti-mb-1 antibody. Mice immunized with this material have produced a strong polyclonal response, so that it should now be possible to prepare a panel of new mAb reactive with different epitopes on both mb-1 and on its associated polypeptide(s).     

The membrane IgM-associated heterodimer on human B cells is a newly defined B cell antigen that contains the protein product of the mb-1 gene

7/8embrane IgM (mIgM) on human B lymphocytes is noncovalently associated with a disulfide-linked dimer that contains phosphoproteins of 47 and 37 kDa. In this study, the biochemical properties and the identity of these Ag receptor-associated components have been addressed. Both subunits carry N-linked carbohydrate groups. After deglycosylation, the 47-kDa and 37-kDa proteins have similar molecular masses, of about 23 kDa, and relatively acidic but different isoelectric points. The accumulated data, together with a previously performed comparison of tryptic peptides, suggest that the two components are structurally distinct and possibly encoded by different genes. Indeed, a mAb, raised against a synthetic peptide that was made on the basis of the published carboxyl-terminal amino acid sequence of the human mb-1 gene product, specifically reacted with the 47-kDa but not the 37-kDa subunit. None of the established B cell-specific mAb characterized in the Fourth International Workshop on Leukocyte Antigens, including CD24, CD37, and CD72, detect the mIgM-linked heterodimer, which makes it a newly defined human B cell Ag.     

甘肃花椒树上天牛一新种（鞘翅目：天牛科）

扁腿天牛属Nortia属于天牛亚科Cerambycinae,目前共知8种(含本文新种),仅分布于亚洲。我国已知4种,分布于甘肃省南部、海南省、台湾省及香港等地。本文记述为害花椒树的天牛一新种。甘肃省武都地区多种经营研究所提供标本,买国庆同志拍摄照片,在此一并致谢。模式标本保存于中国科学院动物研究所。     

Electron transfer in chromaffin-vesicle ghosts containing peroxidase.

In chromaffin vesicles, the enzyme dopamine beta-monooxygenase converts dopamine to norepinephrine. It is believed that reducing equivalents for this reaction are supplied by intravesicular ascorbic acid and that the ascorbate is regenerated by importing electrons from the cytosol with cytochrome b-561 functioning as the transmembrane electron carrier. If this is true, then the ascorbate-regenerating system should be capable of providing reducing equivalents to any ascorbate-requiring enzyme, not just dopamine beta-monooxygenase. This may be tested using chromaffin-vesicle ghosts in which an exogenous enzyme, horseradish peroxidase, has been trapped. If ascorbate and peroxidase are trapped together within chromaffin-vesicle ghosts, cytochrome b-561 in the vesicle membrane is found in the reduced form. Subsequent addition of H2O2 causes the cytochrome to become partially oxidized. H2O2 does not cause this oxidation if either peroxidase or ascorbate are absent. This argues that the cytochrome is oxidized by semidehydroascorbate, the oxidation product of ascorbate, rather than by H2O2 or peroxidase directly. The semidehydroascorbate must be internal because the ascorbate from which it is formed is sequestered and inaccessible to external ascorbate oxidase. This shows that cytochrome b-561 can transfer electrons to semidehydroascorbate within the vesicles and that the semidehydroascorbate may be generated by any enzyme, not just dopamine beta-monooxygenase.     

Full-length sequence of the cDNA for human erythroid beta-spectrin

Spectrin is the major molecular consituent of the red cell membrane skeleton. We have isolated overlapping human erythroid beta-spectrin cDNA clones and determined 6773 base pairs of contiguous nucleotide sequence. This includes the entire coding sequence of beta-spectrin. The sequence translates into a 2137 amino acid, 246-kDa peptide. beta-Spectrin is found to consist of three distinct domains. Domain I, at the N terminus, is a 272-amino acid region lacking resemblance to the spectrin repetitive motif. Sequences in this region exhibit striking sequence homology, at both nucleotide and amino acid levels, to the N-terminal "actin-binding" domains of alpha-actinin and dystrophin. Between residues 51 and 270 there is 55% amino acid identity to human dystrophin, with only four single amino acid gaps in alignment. Domain II consists of 17 spectrin repeats. Several sequence variations are observed in typical repeat structure. Homology to alpha-actinin extends beyond domain I into the N-terminal portion of domain II. Domain III, 52 amino acid residues at the C terminus, does not adhere to the spectrin repeat motif. Combining knowledge of spectrin primary structure with previously reported functional studies, it is possible to make several inferences regarding structure/function relationships within the beta-spectrin molecule.     

Antigen-specific clones of proliferating T lymphocytes. I. Methodology, specificity, and MHC restriction

In this report we describe in detail a new method for cloning antigen-specific, proliferating T lymphocytes directly from primed murine lymph nodes after 3 days of activation in vitro. After expansion in liquid culture the cells from the colonies were shown to be antigen specific and to require I-A histocompatible, irradiated spleen cells for stimulation. For hapten-carrier-type antigens, the T cells were shown to be carrier specific in their recognition but they were also capable of distinguishing the presence of the hapten. Recloning of small numbers of these cells in soft agar under conditions of high plating efficiency yielded true clones (i.e., populations derived from a single cell) whose antigen specificity was identical to that of cells from the original colony. The fact that a clone of T cells was I-A restricted in its antigen recognition demonstrates that suppressor T cell function cannot account for the phenomenon of major histocompatibility complex restriction.     

A simple, rapid, and sensitive method of determining CSF IgG, using latex

A simple, rapid and sensitive method of determining cerebrospinal fluid IgG is presented. The procedure depends upon the fact that spinal fluid gamma globulin, and two of its components (IgG and IgM) will precipitate latex particles in proportion to their concentration, and that the optical density of the supernatant solution containing unprecipitated latex particles after centrifugation is inversely proportional to the concentration of these immunoglobulins. The method is sensitive to 50 nanograms, is inexpensive, requires 0.1 ml. or less of spinal fluid, and can be performed in minutes. Preliminary studies show that it compares favorably with results obtained by radial immunodiffusion.     

Physico-chemical properties of deoxyribonucleoprotamine from sturgeon sperm heads]

Deoxyribonucleoprotamine (DNPn) from sonicated nuclei of sturgeon sperm heads was studied by means of ring dichroism. A derivative analysis of DNA and DNPn melting curves in 1 mM Tris. HCl pH 8.0 revealed the fraction of protein-free DNA being about 30% and suggested the preferable binding of protamine molecules with AT-rich DNA regions. The latter is also confirmed by the data on ring dichroism of protein-poor soluble DNAPn fraction in 0,14 M NaCl. Ring dichroism of DNA and DNPn in 1 mM Tris coinsides at the wavelength of 310-240 nm at concentrations of 500-50 mkg/ml. Dilution of DNPn to 5 mkg-ml resulted in the decrease of the ellipticity at 275 nm and produced no effect at 260-210 nm. The effect observed is suggested to be due to a partial transition of DNA in DNPn into C-form under the dilution as a result of a higher molecule hydration and a destruction of some hydrogen bonds between guanidine residues of arginine and oxygen of phosphate groups, stabilyzing DNA in the B-form. Ring dichroism spectrum of protamine, calculated by the subtraction of DNA spectrum from DNPn spectrum at the region of 240-210 nm coinsides with that of free protamine and indicates the absence of an ordered structure in protamine molecules in DNPn.