The immunological and structural comparisons of deoxyribonucleases I. Glycosylation differences between bovine pancreatic and parotid deoxyribonucleases

A rabbit antiserum against bovine pancreatic DNase A is used to study the immunological reaction of DNases I. As shown by double immunodiffusion, bovine pancreatic DNases A, B, C, and D are immunologically identical, so are DNases from bovine pancreas and parotid and from ovine pancreas. These DNases also behave similarly in immunotitration of DNase activity and all are tightly bound to the immunoaffinity medium, requiring an acidic buffer with 10% ammonium sulfate to dissociate. On the other hand, porcine pancreatic and malted barley DNases that do not form precipitin lines remain active in solution with the antibody; however, in spite of the lack of inhibition these DNases are retarded (but not tightly bound) in immunoaffinity chromatography, suggesting interaction with the antibody. In thin layer isoelectric focusing, the parotid DNase, purified with the immunoaffinity technique, shows only two major active components whose isoelectric points correspond to those of DNases A and C of bovine pancreas. As estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the molecular weight of parotid DNase is 34,000, approximately 3,000 more than that of the pancreatic enzyme. However, both parotid and pancreatic DNases have the same NH2-terminal leucine, an identical COOH-terminal amino acid sequence, nearly identical amino acid compositions, and almost the same peptide maps. The molecular weight difference is due to differences in the carbohydrate side chains. Results of peptide analyses indicate that parotid DNase contains two glycopeptides; pancreatic DNase has only one. In addition, both parotid glycopeptides contain glucosamine and galactosamine while the pancreatic glycopeptide has only glucosamine.     

Membrane Potentials of Heterotrophically Cultured Tobacco Cells

The electrophysiological properties of the membrane of Nicotianatabacum var. Sarnsun cultured cells were determined using amicroelectrode technique in standard medium containing 1 mMKC1, 1 mM NaCl and 1 mu CaCl₂ at pH 7. Tobacco callus was derivedfrom the pith (E_m=–104.4%16.2 mV). The membrane potentialsof the callus cells did not show a symmetrical Gaussian distributionbut were scattered over a wide range. The percentage of highmembrane potential cells increased as the subculture was continueduntil about 11 months and then decreased. The response of themembrane potential to electric stimulus, ionic composition,metabolic inhibitors, sugars and amino acids was characteristicof high (E_m=–{small tilde}–160 220 mV; H-cells)and low (E_m=–80{small tilde}–90 mV; L-cells) membranepotential cells. The membrane potential of H-cells was largelydepolarized by addition of CN^–, carbonium cyanide m-chlorophenylhydrazone,decyclohexylcarbodiimide, and triphenyltin chloride and transientlydepolarized by addition of glucose, galactose, mannose or sucrose,and D-alanine, L-alanine or Llysine, but the membrane potentialof L-cells was not. (Received December 3, 1982; Accepted March 16, 1983)     

The occurrence of polysialogangliosides including ganglio-N-tetraose series in adult bovine nasal cartilage

We extracted glycolipids from adult bovine nasal cartilage and purified some glycolipids by DEAE-Sephadex A-25 and Iatrobeads column chromatography. Cartilage contained 20 nmol of lipid bound sialic acid per gram wet tissue. The relative content of mono, di, tri, and tetrasialo gangliosides were 14%, 40%, 28% and 18%, respectively, as sialic acid content. We characterized some by examining carbohydrate composition, methylation analysis, sialidase treatment and mild acid hydrolysis. The ganglio-N-tetraose series, including GDla, GDlb, GTla, GTlb and GQlb, was identified as one of the major ganglioside groups of this cartilage.     

Amino acid sequence of the active site of human pseudocholinesterase

The usualE ₁ ^u and atypicalE ₁ ^a human pseudocholinesterases (acylocholine acylhydrolase, EC 3.1.1.8) were purified to homogeneity. The active-site serine residue was conjugated with diisopropyl fluorophosphate and digested with trypsin. The tryptic peptide containing the active site was isolated by gel filtration followed by two-dimensional paper chromatography and electrophoresis. The amino acid sequence of the active site peptide obtained from the usualE ₁ ^u enzyme was found to be Gly-Glu-Ser-Ala-Gly-Ala-Ser-Ala-Val-Ser-Leu. A remarkable structural homology exists between the human and the horse enzymes in their active sites. From the difference in electrophoretic mobility of the active-site peptides obtained from the usual and atypical enzymes, the probable structure of the atypical human enzyme was deduced as Gly-His-Ser-Ala-Gly-Ala-Ser-Ala-Val-Ser-Leu.     

A new class of rapidly developing mutants in Dictyostelium discoideum: implications for cyclic AMP metabolism and cell differentiation

Rapidly developing (rde) mutants of Dictyostelium discoideum, in which cells precociously differentiated into stalk and spore cells without normal morphogenesis, were investigated genetically and biochemically. Genetic complementation tests demonstrated that the 16 rde mutants isolated could be classified into at least two groups (groups A and C) and that the first described rde mutant FR17 (D. R. Sonneborn, G. J. White, and M. Sussman, 1963, Dev. Biol. 7, 79-93) belongs to group A. Morphological studies revealed several differences in development and final morphology between group A and group C mutants. In group A mutants, the time required for cell differentiation from vegetative cells to aggregation competent cells is reduced, whereas the time required for spore and stalk cell differentiation following the completion of aggregation is shortened in group C mutants. This suggests that group C mutants represent a new class of rde mutants and that there exist at least two mechanisms involved in regulating the timing of development in D. discoideum. Measurements of cell-associated and extracellular phosphodiesterase activities, and intracellular and total cAMP levels revealed that cAMP metabolism in both groups is significantly altered during development. Group A mutants showed precocious and excessive production of phosphodiesterase and cAMP during the entire course of development; intracellular cAMP levels in group C mutants were extremely low, and spore and stalk cell differentiation occurred without an apparent increase in these levels. Thus, while cAMP metabolism is abnormal in all the rde mutants studied, there exist several distinct types of derangement, not necessarily involving the overproduction of cAMP.     

Clostridium perfringens: I. Sporulation in a Biphasic Glucose-Ion-Exchange Resin Medium

A biphasic culture medium suitable for cultivation and sporulation of Clostridium perfringens, C. botulinum, and C. sporogenes was devised. The medium designed for use in a disposable, compartmented, plastic film container contained peptones, yeast extract, minerals, an anion exchange resin, and glucose in 4% agar as the solid phase and (NH(4))(2)SO(4) and 0.1% agar as the liquid phase. With the biphasic system, it was not necessary to use active cultures as inocula. Growth was at least equal to that obtained in conventional media, and spore production of 9 out of 12 strains of C. perfringens equalled or usually exceeded that of conventional media.     

Alkaline phosphatase from pig kidney. Microheterogeneity and the role of neuraminic acid

Several alkaline phosphatases (EC 3.1.3.1) could be obtained from pig kidney brush-border membrane on extraction with butan-1-ol. Three of the multiple forms were separated by DEAE-cellulose chromatography and further purified. They form a regular series with different degrees of glycosylation (mainly owing to N-acetylneuraminic acid), of charge, of molecular weight, of stability to temperature, to pH and to urea, of minimal requirement for Mg²⁺ and of extractability by butan-1-ol. In contrast, the detectable antigenic sites, the inhibition by amino acids and the pH-dependency of K_m and V_max. were identical for these multiple forms. On treatment with neuraminidase, the multiple forms became identical in all their properties. It was therefore concluded that the microheterogeneity of alkaline phosphatase is due to different degrees of glycosylation at polypeptide chains which appear to be otherwise identical.