Genetic recombination in Micromonospora rosaria by protoplast fusion

Auxotrophic strains of Micromonospora rosaria were isolated by N-methyl-N'-nitro-N'-nitrosoguanidine mutagenesis and used in intraspecific recombination by protoplast fusion. High-frequency fusion of protoplasts of M. rosaria strains was induced by polyethylene glycol (molecular weight, 1,000) (PEG 1,000). The optimum concentration of PEG 1,000 for fusion of M. rosaria was 50% (wt/vol). PEG 4,000 was slightly better than PEG 1,000 at concentrations lower than 50% (wt/vol). The recombinant frequency did not increase after treatment with PEG 1,000 (50% [wt/vol]) for longer than 20 min. Under these conditions, fusion with many auxotrophic strains of M. rosaria resulted in a high frequency of formation of true recombinants (sometimes more than 10%). Additionally, when ros (rosamicin nonproducing) strains were crossed by protoplast fusion; about 5% of the resultant prototrophic recombinants were shown to have the ros+ (rosamicin producing) characteristic restored. Rosamicin production by M. rosaria colonies was clearly distinguished by the broth overlay method. The results of fusion experiments between ros and ros+ strains indicated that either the chromosomal mutation or pleiotrophic effect of some auxotrophic markers is involved.     

Bacillus subtilis alkaline phosphatases III and IV. Cloning, sequencing, and comparisons of deduced amino acid sequence with Escherichia coli alkaline phosphatase three-dimensional structure

Bacillus subtilis has an alkaline phosphatase multigene family. Two members of this gene family, phoAIII and phoAIV, were cloned, taking advantage of in vitro constructed strains containing a plasmid insertion within one or the other of the structural genes. The DNA sequences of the two genes showed approximately 64% identity at the DNA level and 63% identity in the deduced primary amino acid sequences. The phoAIII and phoAIV genes code for predicted proteins of 47,149 and 45,935 Da, respectively. Comparison of the deduced primary amino acid sequence of the mature proteins with other sequenced alkaline phosphatases from Escherichia coli, yeast, and humans shows 25-30% identity. Based on the refined crystal structure of E. coli alkaline phosphatase, it appears that the active site and the core of the structure are retained in both Bacillus alkaline phosphatases. However, both proteins are truncated at the amino terminus compared with other mature alkaline phosphatases, three sizable surface loops of E. coli are deleted, and a minidomain is replaced with a larger domain in the model. Neither Bacillus alkaline phosphatase sequenced contains any cysteine residues, an amino acid implicated in intrachain disulfide bond formation in other alkaline phosphatases.     

Identification of sphingomyelin turnover as an effector mechanism for the action of tumor necrosis factor alpha and gamma-interferon. Specific role in cell differentiation.

The biochemical signaling mechanisms involved in transducing the effects of tumor necrosis factor alpha (TNF alpha) and gamma-interferon (gamma-IFN) on leukemia cell differentiation are poorly defined. Recent studies established the existence of a sphingomyelin cycle that operates in response to the action of vitamin D3 on HL-60 cells and that may transduce the effects of vitamin D3 on cell differentiation (Okazaki, T., Bell, R., and Hannun, Y. (1989) J. Biol. Chem. 264, 19076-19080). The effects of TNF alpha and gamma-IFN on sphingomyelin turnover were determined, and the specificity and role of sphingomyelin hydrolysis in HL-60 human promyelocytic leukemia cells with 20% hydrolysis of sphingomyelin at 15 min, 40% hydrolysis at 30-60 min, and return to base line at 2 h. The hydrolyzed sphingomyelin (18 pmol/nmol total phospholipid) was accompanied by the concomitant generation of ceramide (11.2 pmol/nmol total phospholipid). gamma-IFN also caused reversible hydrolysis of sphingomyelin with onset at 1 h and peak effect at 2 h. This sphingomyelin cycle appeared to be specific to the monocytic pathway of HL-60 differentiation, since it was not activated by retinoic acid or dibutyryl cAMP, inducers of granulocytic differentiation, nor with phorbol myristate acetate, an inducer of macrophage-like differentiation. Addition of synthetic ceramide or bacterial sphingomyelinase induced monocytic differentiation of HL-60 cells. Cell-permeable ceramide also caused prompt down-regulation of mRNA for the c-myc protooncogene. The time course of c-myc down-regulation was consistent with the action of ceramide as the mediator of TNF alpha action. These results suggest that sphingomyelin turnover may be an important signaling mechanism transducing the actions of TNF alpha and gamma-IFN with specific function in cell differentiation.     

Nucleotide sequence of the R721 shufflon.

The shufflon is a DNA region that undergoes complex rearrangement mediated by the product of a putative site-specific recombinase gene, rci. The DNA sequences of the shufflon region and the rci gene of IncI2 plasmid R721 were determined. The R721 shufflon consists of three invertible DNA segments that are homologous to the shufflon segments found in IncI1 plasmid R64. Structural analysis of open reading frames indicated that the R721 shufflon possibly functions as a biological switch for selecting one of the six pilV genes in which the N-terminal region is constant and the C-terminal region is variable. The R721 rci gene was shown to encode a basic protein of 374 amino acid residues.     

Analysis of the importance of arginine 102 in neutral endopeptidase (enkephalinase) catalysis.

Neutral endopeptidase 24.11 contains an active site arginine believed to function in substrate binding. This arginine is thought to form an ionic interaction with the COOH-terminal carboxylate of NEP substrates. The functionality of arginine 102 has been investigated by using site-directed mutagenesis to produce mutants in which this residue was converted to a lysine, glycine, glutamine, or glutamate. All of the mutants exhibited essentially full activity as determined with a synthetic peptide amide, glutaryl-Ala-Ala-Phe-4-methoxy-2-naphthylamide. In contrast, activity was detected only with the wild-type enzyme and the lysine mutant using a synthetic substrate containing a free COOH-terminal carboxylate, dansyl-Gly-Trp-Gly. Inhibition studies with the physiologically active peptide substrates substance P, endothelin, and angiotensin I, as well as substance P free acid, [D-Ala2,Leu5]enkephalin, and [D-Ala2,Leu5]enkephalinamide indicated a lack of importance of arginine 102 in substrate binding. With [D-Ala2,Met5]enkephalin and the chemotactic peptide, N-formyl-Met-Leu-Phe, a significant decrease in affinity is observed with the arginine 102 mutants. These results suggest that the contribution of arginine 102 to substrate binding is dependent upon the strength of other subsite interactions. Examination of dipeptides as inhibitors indicates that the nature and orientation of the P'2 residue is important in determining the strength of the interaction of arginine 102 with its substrates.     

Immunohistochemical localization of 36 and 29 kDa proteins in sparganum.

Antigenic proteins of 36 and 29 kDa were localized in Spirometra mansoni plerocercoid (sparganum) immunohistochemically by avidin biotin complex (ABC) staining. When polyclonal antibodies such as BALB/c mouse serum immunized with crude saline extract of sparganum or confirmed sparganosis sera were reacted as primary antibodies, the positive chromogen (3-amino, 9-ethylcarbazole) reactions were recognized at syncytial tegument, tegumental cells, muscle and parenchymal cells and lining cells of excretory canals. A monoclonal antibody (MAb) which was reacting to 36 and 29 kDa proteins in the extract of the worm was localized at the syncytial tegument and tegumental cells. The present results suggested that the potent antigenic proteins of 36 and 29 kDa in sparganum were produced at the tegumental cells and transported to the syncytial tegument.     

Karyotypes of Pneumocystis carinii from Korean rats.

Molecular karyotyping was applied to Pneumocystis carinii(Pc) from two strains of experimental rats, Sprague Dawley(SD) and Fisher(F), in Korea. Field inversion gel electrophoresis and contour clamped homogeneous electric field electrophoresis resolved 15 chromosomal bands from the Pc. The size of the bands was estimated 270kb to 684kb from SD rats, and 273kb to 713 kb from F rats. The bands of 283 kb from SD rats and of 273 kb from F rats stained more brightly suggesting duplicated bands. Total number of chromosomes was at least 16, and total genomic size was estimated 7 x 10(6) bp. All of the bands from F rats hybridized to the probe of repeated DNA sequences of Pc and the band of 448 kb size was proved to contain rDNA sequences, but Pc. chromosome bands from SD rats showed no reactions to the probes. The 2 different karyotypes of P. carinii from 2 strains of rats were maintained consistently for 2 years.     

Changes in Esterification of the Uronic Acid Groups of Cell Wall Polysaccharides during Elongation of Maize Coleoptiles

Cell walls of grasses have two major polysaccharides that contain uronic acids, the hemicellulosic glucuronoarabinoxylans and the galactosyluronic acid-rich pectins. A technique whereby esterified uronic acid carboxyl groups are reduced selectively to yield their respective 6,6-dideuterio neutral sugars was used to determine the extent of esterification and changes in esterification of these two uronic acids during elongation of maize (Zea mays L.) coleoptiles. The glucosyluronic acids of glucuronoarabinoxylans did not appear to be esterified at any time during coleoptile elongation. The galactosyluronic acids of embryonal coleoptiles were about 65% esterified, but this proportion increased to nearly 80% during the rapid elongation phase before returning to about 60% at the end of elongation. Methyl esters accounted for about two-thirds of the total esterified galacturonic acid in cell walls of unexpanded coleoptiles. The proportion of methyl esters decreased throughout elongation and did not account for the increase in the proportion of esterified galactosyluronic acid units during growth. The results indicate that the galactosyluronic acid units of grass pectic polysaccharides may be converted to other kinds of esters or form ester-like chemical interactions during expansion of the cell wall. Accumulation of novel esters or ester-like interactions is coincident with covalent attachment of polymers containing galactosyluronic acid units to the cell wall.