Cellular localization of bovine pancreatic trypsin inhibitor and related molecular forms in bovine lung

Summary In addition to bovine pancreatic trypsin inhibitor (BPTI), three BPTI-related molecular forms (isoinhibitors I, II and III) were isolated from bovine lung by affinity chromatography on immobilized trypsin and subsequently purified by Fast Protein Liquid Chromatography. These inhibitors are identical to the isoinhibitors previously isolated from bovine spleen. Their localization in bovine lung was studied by immunohistochemical techniques, using two different immunoglobulin preparations, selectively recognizing BPTI or the other molecular forms.BPTI-related immunoreactivity was found to be restricted to isolated cells, often identified as mast cells by Toluidine Blue staining. In contrast, isoinhibitor-related immunoreactivity, which also occurs in the mast cells, is present in a number of other cell types. These types include: (i) the smooth muscle cells of different calibre vessels, (ii) the ciliated cells of the bronchial epithelium and the related mucus, and (iii) many cells at alveolar level.Comparison of these data with previous results obtained for bovine spleen suggest multiple physiological roles for these inhibitors.     

Effect of Naturally Occurring nif Reiterations on Symbiotic Effectiveness in Rhizobium phaseoli

Most naturally occurring strains of Rhizobium phaseoli possess reiteration of the nif genes. Three regions contain nitrogenase structural genes in strain CFN42. Two of these regions (a and b) have copies of nifH, nifD, and nifK, whereas the third region (c) contains only nifH. Strains containing mutations in either nif region a or nif region b had significantly diminished symbiotic effectiveness compared with the wild-type strain on the basis of nodule mass, total nitrogenase activity per plant, nitrogenase specific activity, total nitrogen in the shoot, and percentage of nitrogen. A strain containing mutations in both nif region a and nif region b was totally ineffective. These data indicate that both nif region a and nif region b are needed for full symbiotic effectiveness in R. phaseoli.     

Microcin-E492-insensitive mutants of Escherichia coli K12

Mutations in three Escherichia coli K12 genes, tonB, exbB and the newly discovered semA, reduce sensitivity to the low Mr polypeptide antibiotic microcin E492. The products of the tonB and exbB genes were previously shown to be involved in the uptake of siderophore-complexed iron and in the action of a number of colicins. Strains mutated at or close to semA (collectively referred to as sem mutations) remained fully sensitive to these colicins, and grew as well as wild-type strains under conditions of iron starvation. Expression of a number of sem-lacZ operon fusions was not affected by iron limitation, and sem mutations did not affect the production of iron-regulated outer membrane proteins which are known or thought to be involved in iron uptake. Hfr conjugation and P1 phage transduction experiments indicated that semA is located close to pabB at 40 min on the E. coli K12 chromosome. This places semA close to the mng locus, wherein mutations result in decreased manganese sensitivity. However, strains carrying the semA mutation exhibited increased manganese sensitivity.     

The primary structure of human hemopexin deduced from cDNA sequence: evidence for internal, repeating homology.

We have cloned and analyzed a cDNA containing the coding sequence for human hemopexin. We have first identified, by immunological screening of 30.000 colonies of a liver cDNA library in the expression vector pEX1, a clone carrying an insert 1170 base pairs long that shows 100% homology with a known human hemopexin peptide. The complete sequence coding for hemopexin was isolated from a liver cDNA library in the vector pAT218. The DNA insert of 1523 base pairs shows an open reading frame coding for 439 amino acids, a 3' noncoding region of 159 nucleotides long, followed by a poly(A) tail. The insert spans the entire coding region and from which the primary structure of the protein was deduced. By computer assisted analysis of the amino acid sequence, it was possible to recognize a core unit, of about 45 amino acids, which is repeated 8 or possibly even 10 fold along the polypeptide chain. This feature suggests that the gene might have evolved through a series of duplications. This characteristic, together with prediction of secondary structure, suggest a rough model for the tridimensional folding that allows some speculations on the function of hemopexin. Blot hybridization of total RNA from human liver with nick translated hemopexin cDNA detected a message of about 1600 nucleotides. Southern blot experiments to identify the hemopexin gene (s) suggest that it is not a large multi-gene family, but that there is only one or at most a few genes in the human genome.     

Autophosphorylation of type 2 casein kinase TS at both its α- and β-subunits: Influence of different effectors

Rat liver casein kinase TS (Ck-TS) having quarternary structure α₂β₂, autophosphorylates at its 25 kDa, β-subunits, incorporating up to 1.2 mol P/mol enzyme. According to their effects on the autophosphorylation pattern the effectors of Ck-TS activity can be grouped into 3 classes: (i) inhibitors, like heparin, which also prevent the autophosphorylation of the β-subunit; (ii) stimulators possessing several amino groups (like spermine) which increase the autophosphorylation at the β-subunit; (iii) stimulators possessing several guanido groups, like protamines and related peptides, which prevent the phosphorylation of the β-subunit, while promoting the autophosphorylation of the 38 kDa α-subunit. In the presence of such polyarginyl effectors the 130 kDa Ck-TS is converted into forms with higher sedimentation coefficient.     

Regulation of lipogenesis in vivo by glucose availability and insulin secretion in maternal and foetal tissues during late gestation in the rat. Effect of glucose intubation, streptozotocin-induced diabetes and starvation.

Administration of an oral load of glucose did not change the rate of lipogenesis in maternal liver during late gestation. However, streptozotocin-induced diabetes or starvation decreased maternal liver lipogenesis at 20-22 days of gestation. Glucose intubation, on the other hand, increased foetal lipogenesis at 21-22 days. In addition, maternal starvation decreased foetal lipogenesis and plasma insulin concentration. However, chronic hyperglycaemia induced by streptozotocin administration to the mother did not change foetal liver lipogenesis.     

Operon fusions of Mu d1(Ap,lac) to thel-proline biosynthetic genes ofescherichia coli K-12

Operon fusions to the promoter of either theproA,proB, orproC genes of the proline biosynthetic pathway were obtained by the use of the Mu d1(Ap,lac) bacteriophage. These fusions were further stabilized by transformation with plasmid pGW600 containing the wildtype Mu repressor gene or by transduction with phage pSG1. The level of -galactosidase in the fusion strains was not affected by the presence of exogenously addedl-proline or high concentrations of NaCl in the growth medium. A Tn5 insertion nearproBA increased -galactosidase expression 140- to 200-fold in strains carrying theproA-lac andproB-lac fusions, but the level of this enzyme was unaltered in strains carrying theproC-lac fusion. The Tn5 insertion increased intracellular proline concentrations 8- to 10-fold, suggesting that mechanisms other than allosteric inhibition may regulate proline biosynthesis, but did not confer osmotolerance to cells growing in a medium with a high concentration of salt.