Target sizes of human erythrocyte membrane Ca2+-ATPase and Mg2+-ATPase activities in the presence and absence of calmodulin

We have investigated the subunit structure of Ca2+-transport ATPase in human erythrocyte membranes using radiation inactivation analysis. All inactivation data were linear on a semilog plot down to at least 20% of the control activity. We found a target size for the calmodulin-dependent Ca2+-ATPase activity of 331 kDa, consistent with the presence of this enzyme as a dimer in calmodulin-depleted ghosts. Membranes which had been saturated with calmodulin before irradiation yield a a similar size of 317 kDa, implying that activation of Ca2+-transport ATPase by calmodulin does not involve significant change in oligomeric structure. Basal (calmodulin-independent) Ca2+-ATPase activity corresponded to a size of 290 kDa, suggesting that this activity resides in the same, or similar-sized, complex as the calmodulin-dependent activity. Mg2+-ATPase activity, however, was found to reside in a smaller complex of 224 kDa, which proved to be statistically distinct from the target size of Ca2+-ATPase activity. It would appear that Mg2+-ATPase is a distinct entity whose function is likely unrelated to the Ca2+-transport ATPase.     

Structural transitions of chromatin at low salt concentrations: a flow linear dichroism study

We have studied the structure of nuclease-solubilized chromatin from Ehrlich ascites cells by flow linear dichroism (LD) using the anisotropic absorption of the DNA bases and of two intercalated dyes, ethidium bromide and methylene blue. It is confirmed that intercalation occurs preferentially in the linker part of the chromatin fiber, at binding ratios (dye/base) below 0.020. Using this information, we determined the orientation of the linker in relation to the average DNA organization in chromatin. The LD measurements indicate that the conformation of chromatin is considerably changed in the ionic strength interval 0.1-10 mM NaCl: with increasing salt concentration, the LD of the intrinsic DNA base absorption changes signs, from negative to positive, at approximately 2.5 mM NaCl. The LD of the intercalated dyes also changes signs, however, at a somewhat higher salt concentration. The results are analyzed in terms of possible allowed combinations of tilt angles of nucleosomes and pitch or tilt angles of linker DNA sections relative to the fiber axis, at different salt concentrations in the interval 0.1-10 mM NaCl. Two models for the salt-induced structural change of chromatin are discussed.     

Association of the M blood group system with bovine mastitis

Associations of the 11 bovine blood group systems with mastitis were examined in Red Danish dairy cattle. The mastitis status was followed during three lactational periods. A significant effect of the M blood group system on mastitis incidence was observed in the first and second lactation periods and a lower frequency of mastitis is found among animals lacking the M' factor as compared to those having the M' blood group factor. The significance of these results are discussed in view of the close relation between the M blood group system and the bovine lymphocyte antigens (BoLA), and the expected effect of eliminating the M' gene from the breed is estimated. Among the remaining 10 blood group systems, the T' system was the only system showing an overall effect on mastitis, and only in first and third lactation. However, the T' system was inconsistent with regard to the effect of the T' gene on the various mastitis diagnoses.     

Immunocytochemical demonstration of tissue-type plasminogen activator in endocrine cells of the rat pituitary gland

We immunocytochemically stained rat pituitary glands using antibodies against plasminogen activators of the tissue type (t-PA) and the urokinase type (u-PA). A large population of endocrine cells in the anterior lobe of the gland displayed intense cytoplasmic immunoreactivity with anti-t-PA. In some areas of the intermediate lobe we found a weak staining, and we observed weakly staining granular structures in the posterior lobe. Controls included absorption of the antibodies with highly purified t-PA. In addition, SDS PAGE followed by immunoblotting of pituitary gland extracts revealed only one band with an electrophoretic mobility similar to that of t-PA when stained with anti-t-PA IgG. No u-PA immunoreactivity was detected in the rat pituitary gland. Sequential staining experiments using antibodies against growth hormone and t-PA demonstrated that the t-PA-immunoreactive cells constitute a large subpopulation of the growth hormone-containing cells. These findings represent the first direct evidence for the presence of t-PA in cell types other than endothelial cells in the intact normal organism. In this article we discuss the implications of the results for a possible role of t-PA in the posttranslational processing of prohormones.     

Plasminogen and tissue-type plasminogen activator bind to immobilized fibronectin

Fibronectin immobilized onto polystyrene surface was found to bind plasminogen and tissue-type plasminogen activator (t-PA) but only slightly the urokinase type as determined using mono- and polyclonal antibodies against the activators. Of the defined fibronectin fragments tested, the Mr 120,000-140,000 fragment was found to bind both plasminogen and t-PA. Proteolytically modified plasminogen (Lys-plasminogen) bound considerably better than the native form (Glu-plasminogen). Experiments with 125I-plasminogen yielded Kd = 9.1 X 10(-8) M for the binding to immobilized fibronectin. The partially or completely inactive single-chain form of t-PA (pro-t-PA) bound considerably better than the activated two-chain form. Lysine at greater than 3 mM inhibited the binding of plasminogen. The interaction was independent of calcium ions. CaCl2 (greater than 0.5 mM) and NaCl (greater than 0.2 M) inhibited the binding of pro-t-PA and of t-PA. Fibronectin-bound t-PA retained its ability to activate plasminogen. The observed interactions may operate in directional proteolysis localizing plasminogen and plasminogen activator to degrade fibronectin-containing extracellular matrix including fibrin clots.     

Identification and characterization of DNA clones encoding group-II glycinin subunits

Summary DNA clones that encode the group-II subunits of soybean glycinin were identified and compared with clones for group-I subunits. The group-I clones hybridize weakly to those from group-II at low stringency, but fail to hybridize with them at moderate or high stringency. The genes for the group-II subunits are contained in 13 and 9 kb EcoRI fragments of genomic DNA in cultivar CX635-1-1-1. These fragments contain genes for subunits A₅A₄B₃ and A₃B₄, respectively. The larger size of mature group-II subunits compared with group-I subunits is correlated with a larger sized mRNA. However, the gross arrangement of introns and exons within the group-II coding regions appears to be the same as for the genes which encode group-I subunits. Messenger RNA for both groups of glycinin subunits appear in the seed at the same developmental interval, and their appearance lags slightly behind that of mRNAs for the a/a subunits of -conglycinin. These data indicate that the glycinin gene family is more complex than previously thought.Abbreviations bp base pairs - kb kilobase pairs - SDS sodium dodecyl sulfate Cooperative research between USDA/ARS and the Indiana Agric. Expt. Station. This work was supported in part by grants from the USDA Competitive Grants Program and the American Soybean Association Research Foundation. This is Journal Paper No. 10,078 from the Purdue Agricultural Experiment Station     

Effects in chicks of arsenic,arginine, and zinc and their interaction on body weight,plasma uric acid,plasma urea,and kidney arginase activity

The interaction among arsenic, zinc, and arginine was studied in chicks using two fully crossed, three-way, two-by-two-by-two experiments. Arsenic at levels of 0 and 2 μg/g zinc at levels of 2.5 (zinc-deficient) and 25 (zinc-adequate) μg/g, and arginine at levels of 0 and 16 mg/g were supplemented to the diet. After 28 d in both experiments, growth was depressed in chicks fed diets either supplemented with arginine or deficient in zinc. Arsenic deprivation depressed growth of chicks fed diets containing the basal level of arginine and 25 μg supplemental Zn/g. Arsenic deprivation had little or no effect on growth of zinc-deprived chicks fed diets containing the basal level of arginine, or in zinc-deprived or zinc-adequate chicks fed supplemental arginine. Zinc-deficiency elevated urea in plasma and arginase activity in kidney. Those elevations, however, were more marked in arsenic-supplemented than in arsenic-deprived chicks. Also, plasma urea and kidney arginase activity were markedly elevated in chicks fed supplemental arginine; the elevations were more marked in zinc-deficient chicks. These findings support the concept that arsenic has a physiological role, associated with zinc, that can influence arginine metabolism in the chick.     

Simplified purification and testing of colloidal gold probes

A novel efficient method for purifying and testing colloidal gold probes has been developed. The method consists of concentrating colloidal gold particles conjugated to IgG or protein A in dialysis bags over silica gel and purifying them by gel chromatography on small columns of Sephacryl S-400. Fractions collected are tested by paper immunocytochemical models. Comparisons to gold probes purified by conventional ultracentrifugation documents that ultrastructural staining intensities and total yield of gold probes is the same, but that the chromatographically purified gold probes are less prone to aggregation or clumping. The method has been extensively used for preparing conjugates of 5, 10 or 15 nm gold particles with antirabbit immunoglobulins but has also been exploited for preparing streptavidin-gold conjugates, protein A-gold conjugates and antirabbit immunoglobulin-silver conjugates.