Association of a Ras-related protein with cytochrome b of human neutrophils

Activation of the superoxide generating system in human neutrophils is thought to involve the interaction or assembly of cytochrome b with other cytosolic and membrane proteins. We have now co-isolated by conventional purification procedures a protein of relative molecular mass 22,000 with cytochrome b. This Ras-related protein is not a fragment of either of the subunits of cytochrome b, and its primary structure, as determined by the sequencing of its complementary DNA, is identical to that predicted from a recently cloned ras-related gene, rap1 (also termed Krev-1). Immunoaffinity purification on anti-cytochrome and anti-Ras immunoaffinity matrices indicates an association between cytochrome b and the Ras-related protein. The association of a Ras-related GTP-binding protein with cytochrome b of human neutrophils could indicate a role for such a protein in the transduction, regulation or structure of the superoxide generating system.     

Normetanephrine and metanephrine oxidized by both types of monoamine oxidase

Summary Both normetanephrine and metanephrine were found to be oxidized by both types of monoamine oxidase in mouse liver mitochondria. Both K_m and V_max values of type B MAO for both substrates were higher than those of type A MAO, which caused the shift of inhibition curves with clorgyline and deprenyl according to the increase in substrate concentration.     

Transformation of mononuclear phagocytes in vivo and malignant histiocytosis caused by a novel murine spleen focus-forming virus

The study of retrovirus-induced leukaemias in mice is a powerful tool for the elucidation of the normal regulation of the haematopoietic system. The acute murine spleen focus-forming viruses (SFFV) can be classified according to the haematopoietic lineage on which they exert their effects in the adult mouse. Here we report a new SFFV isolate, the AF-1 virus, with the novel ability to transform cells of the mononuclear phagocyte lineage. The virus was isolated from sarcomas that were induced on passage of a cloned Friend helper virus (F-MuLV, 643/22F) in newborn BALB/c mice. We have cloned the transforming defective subunit of the AF-1 viral complex in NRK cells and isolated several subclones. Analysis of the proviral genome in two non-producer cell clones reveals that AF-1 virus contains Harvey v-ras-specific sequences (Fig. 1). Thus, AF-1 virus is closely related to Harvey murine sarcoma virus (Ha-MSV), and is, at present, the only tool by which permanent cell lines can be obtained from mononuclear phagocytes in the mouse.     

Lymphokine dependence of in vivo expression of MHC class II antigens by endothelium

Changes in the expression of class II antigens of the major histocompatibility complex (MHC) have an integral role in the regulation of immune responses, and are brought about in vitro by soluble mediators. However, the mechanism that underlies in vivo expression of MHC class II antigens in, for example, endothelial cells in the absence of immunological stimulation has not been studied. We demonstrate here that expression of MHC class II antigens is not a constitutive property of endothelial cells, for MHC class II antigen-positive endothelial cells do not express these antigens during treatment with the immunosuppressive agent cyclosporin A. In vivo MHC class II antigen expression by canine endothelial cells is therefore dependent on factors, probably the lymphokine gamma-interferon produced by the immune system, whose secretion is inhibited by cyclosporin A.     

Local protein-DNA interactions may determine nucleosome positions on yeast plasmids

The structure of the nucleosome core particle, the basic structural subunit of chromatin, is well known. Although nucleosomes often appear to be positioned randomly with respect to DNA sequences, in some cases they seem to occupy precisely defined positions on the DNA. The yeast plasmid TRP1ARS1 contains three precisely positioned, stable nucleosomes, I, II and III, which are flanked by nuclease-sensitive regions. Our aim in the present study was to determine whether the positions of these three nucleosomes relate to (1) protein-DNA interactions; (2) the limited space between nuclease-sensitive regions, which is just long enough to accommodate three yeast nucleosomes (that is, boundary conditions); or (3) proximity to the putative origin of replication in one of the nuclease-sensitive regions. We have tested these alternatives by analysing the positions of nucleosomes after insertion of various lengths of DNA into this region and assembly of chromatin in vivo. Our results suggest that specific protein-DNA interactions are the most likely determinants of these nucleosome positions.     

Association of rheumatoid arthritis and primary osteoarthritis with changes in the glycosylation pattern of total serum IgG

Rheumatoid arthritis (RA) is a widely prevalent (1-3%) chronic systemic disease thought to have an autoimmune component; both humoral and cellular mechanisms have been implicated. Primary osteoarthritis (OA) is considered to be distinct from rheumatoid arthritis, and here damage is thought to be secondary to cartilage degeneration. In rheumatoid arthritis, immune complexes are present that consist exclusively of immunoglobulin, implying that this is both the 'antibody' (rheumatoid factor [RF]) and the 'antigen' (most commonly IgG). Autoantigenic reactivity has been localized to the constant-region (C gamma 2) domains of IgG. There is no evidence for a polypeptide determinant but carbohydrate changes have been reported. We have therefore conducted a study, simultaneously in Oxford and Tokyo, to compare in detail the N-glycosylation pattern of serum IgG (Fig. 1) isolated from normal individuals and from patients with either primary osteoarthritis or rheumatoid arthritis. The results, which required an evaluation of the primary sequences of approximately 1,400 oligosaccharides from 46 IgG samples, indicate that: (1) IgG isolated from normal individuals, patients with RA and patients with OA contains different distributions of asparagine-linked bi-antennary complex-type oligosaccharide structures, (2) in neither disease is the IgG associated with novel oligosaccharide structures, but the observed differences are due to changes in the relative extent of galactosylation compared with normal individuals. This change results in a 'shift' in the population of IgG molecules towards those carrying complex oligosaccharides, one or both of whose arms terminate in N-acetylglucosamine. These two arthritides may therefore be glycosylation diseases, reflecting changes in the intracellular processing, or post-secretory degradation of N-linked oligosaccharides.     

Isolation and characterization of hemagglutinins from the sponge Dysidea herbacea

The sponge Dysidea herbacea (Keller) was found to possess hemagglutinins. The major component, DHA-I, is a protein with a mol. wt of 26,000, which dissociates into subunits of equal size (14,000). It contains large amounts of glutamic acid and aspartic acid residues, but no half-cystine, methionine or histidine residues. DHA-I reacted with rabbit and human AB0 erythrocytes. D-galactose and lactose were effective inhibitors of DHA-I. The sponge also contained a minor component(s) which reacted preferentially with rabbit erythrocytes but not with human AB0 erythrocytes.