The primary structure of the beta-subunit of the cell surface adhesion glycoproteins LFA-1, CR3 and p150,95 and its relationship to the fibronectin receptor.

The lymphocyte-function-associated antigen-1 (LFA-1), the complement receptor type 3 (CR3) and the antigen p150,95 are cell-surface glycoproteins. They are heterodimeric complexes, each containing a unique alpha-subunit noncovalently associated with a common beta-subunit. We have purified the beta-subunit from human spleen and obtained limited peptide sequences. What appears to be the complete primary structure for the fully processed beta-subunit was obtained by cDNA sequencing of clones from a phorbol ester (PMA) stimulated U937 cDNA library. There are five possible glycosylation sites and a transmembrane segment. The sequence contains a high level of cysteine (7.6%), with 24 of the 57 cysteine residues being found in three repeating units each with eight residues. The entire primary structure has 47% identity to a subunit of a fibronectin binding protein from chicken fibroblasts. It seems that LFA-1, CR3 and p150,95 antigens may belong to an extended family of cell surface molecules including the fibronectin binding protein.     

Adenosine and oxytocin reverse antagonism of cyclic AMP elevating agents to insulin activation of adipocyte pyruvate dehydrogenase

ACTH, isoprenaline, forskolin, and dibutyryl cyclic AMP prevented insulin from stimulating adipocyte pyruvate dehydrogenase in the presence of adenosine deaminase. Antagonism was reversed by N6-phenylisopropyladenosine as well as oxytocin. The stimulatory effects of insulin, adenosine and oxytocin on adipocyte pyruvate dehydrogenase appear to be through (a) mechanism(s) which is (are) similar or related.     

Complementarity of particles and pits in freeze-fractured hepatic and cardiac gap junctions

Summary Particles and pits of freeze-fractured gap junctions are considered as complementary structures despite the frequent observations of more regular and closer spacings of pits, ascribed to plastic deformation of particle arrays. Recently, however, the noncomplementarity of pits and particles in Purkinje fibers has been reported. To ascertain the relationship between both structures, gap junctions from fixed, cryoprotected liver and myocardium were investigated using spacing and density measurements and complementary replicas.In hepatocyte gap junctions, the center-to-center distances (mean±sd) among pits, 9.57±1.49 nm, and particles, 9.70±1.77 nm, are not significantly different. Density determinations yielded a slightly higher value for the pits, (11,510±830)/m², than for the particles, (11,230±950)/m². In the myocardium, the spacing of the regularly arrayed pits, 9.55±1.33 nm barely exceeds the value of 9.44±1.62 nm for the particles, which show some clustering. However, the packing density for the pits, (10,090±740)/m², appears a little higher than that of the particles (9,890±920)/m². As density and spacing measurements provided no decisive answers, the positions of individual pits and particles of complementary junctional faces were recorded on transparent sheets and compared. In this fashion, a one-to-one correspondence between particles and pits could be established, while small discrepancies may be attributed to plastic deformation. Moreover, the collinearity of pits and particles may be suggested by the observation of a platinum grain in the center of many pits.     

Hepatic lipase: a member of a family of structurally related lipases

Partial amino acid sequence of rat hepatic lipase was obtained by gas-phase microsequence analysis of proteolytic fragments. Sequence comparison to bovine lipoprotein lipase and porcine pancreatic lipase reveals a highly conserved region existing among these three physiologically distinct lipolytic enzymes. In a stretch of 36 amino acid residues previously reported for pancreatic lipase (De Caro, J., Boudouard, M., Bonicel, J., Guidoni, A., Desnuelle, P. and Rovery, M. (1981) Biochim. Biophys. Acta 671, 129-138), nineteen residues are identical for all three enzymes, whereas 27 of 36 are identical in rat hepatic lipase and bovine lipoprotein lipase. The fact that this primary structural conservation extends to three different animal species emphasizes the conclusion that these lipolytic enzymes comprise a protein family originating from a common ancestral gene.     

Genetic transformation of flax (Linum usitatissimum) by Agrobacterium tumefaciens: regeneration of transformed shoots via a callus phase

Genetic transformation of flax (Linum usitatissimum) has been achieved using an A. tumefaciens strain carrying a non-oncogenic Ti plasmid-derived vector containing a chimaeric npt-II gene and a wild type nopaline synthase gene. Fertile, transformed shoots were most easily obtained from Km^r callus developing on hypocotyl sections. The totipotency of the Km^r callus was dependent upon its origin. T-DNA was visualised by Southern blotting in all Km^r tissues. Efficient expression of nopaline synthase and the chimaeric npt-II gene was found in transformed Km^r callus and regenerated shoots.Abbreviations npt-II neomycin phosphotransferase II gene - NPT-II neomycin phosphotransferase II - nos nopaline synthase gene promoter - Km^r kanamycin resistant - BAP 6-benzylaminopurine - NAA -naphthaleneacetic acid - MSD4×2 medium D4×2 based on Murashige & Skoog medium (see Scott & Draper, 1987)