Biosynthesis of D-alanyl-lipoteichoic acid: role of diglyceride kinase in the synthesis of phosphatidylglycerol for chain elongation.

Lipophilic and hydrophilic D-alanyl-lipoteichoic acids are elongated in Lactobacillus casei by the transfer of sn-glycerol 1-phosphate units from phosphatidylglycerol to the poly(glycerophosphate) moiety of the polymer. These sn-glycerol 1-phosphate units are added to the end of the poly(glycerophosphate) which is distal to the glycolipid anchor; 1,2-diglyceride results from this addition. The presence of a diglyceride kinase was suggested by the ATP-dependent phosphorylation of 1,2-diglyceride to phosphatidic acid. Inorganic phosphate was used to initiate the synthesis of lipophilic lipoteichoic acid (LTA) and the elongation of both lipophilic and hydrophilic LTA. Three observations suggest that phosphate and other anions play a role in the in vitro synthesis of LTA and its precursors. First, the conversion of 1,2-diglyceride to phosphatidic acid by diglyceride kinase was stimulated. Second, the synthesis of phosphatidylglycerol was increased. Third, the elongation of lipophilic and hydrophilic LTA was enhanced. These observations indicated that one effect of phosphate might be to enhance the utilization of 1,2-diglyceride for the synthesis of phosphatidic acid. This phospholipid is a precursor of phosphatidylglycerol, the donor of sn-glycerol 1-phosphate for elongation of LTA.     

Application of dual pre-embedding stains for gonadotropins to pituitary cell monolayers with avidin-biotin (ABC) and peroxidase-antiperoxidase (PAP) complexes: light microscopic studies

Double stains for gonadotropins and gonadotropin-releasing hormone were developed for fixed whole pituitary cells from cycling female rats. Monolayer cells were stimulated with [D-Lys6]GnRH, fixed in 2.5% glutaraldehyde, and then stained for luteinizing hormone (LH) (1:50,000-12 h) or follicle stimulating hormone (FSH) (1:60,000-12 h) and the avidin-biotin-peroxidase complex technique (ABC) with a jet-black substrate (nickel intensified diaminobenzidine-DAB). This was followed by a stain for the other gonadotropin with either ABC or peroxidase-antiperoxidase complex (PAP) techniques and amber (DAB) or red (3-amino-9-ethyl-carbazole) substrates. Additional monolayers were stimulated with biotinylated [D-Lys6]GnRH and stained with the ABC technique and the black (nickel-DAB) substrate. These monolayers were then stained immunocytochemically for LH or FSH with either ABC or PAP methods and orange or red substrates. The controls showed that the omission of the second primary antiserum abolished the stain indicating that the second staining solutions did not react with components in the first group. The addition of the second peroxidase substrate in sequence after the first stain indicated that no residual peroxidase activity remained from the first stain. Our tests also showed that saponin was not needed to aid reagent or antibody penetration. The dual stains demonstrated that 50-60% of the gonadotropes stored LH and FSH together, often in separate regions of the same cell. Some cells contained only one hormone (20-22%). The dual stains for GnRH and gonadotropins demonstrated that 80-90% of the GnRH bound cells are gonadotropes. These techniques allow a study of storage sites for multiple hormones in or on whole cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhibition of enzymes by metal ion-chelating reagents. Theory and new graphical methods of study

1. The mechanism of inhibition of enzymes by metal ion-chelating reagents is discussed and equations derived. 2. Two distinct mechanisms are postulated and graphical methods are given for differentiating between them. 3. Where the metal ion is actually removed from the enzyme to form a co-ordination complex in solution, a procedure is described for obtaining the stability constant for metal-enzyme interaction, the number of metal ions involved and the stoicheiometry of metal ion-ligand interaction.     

Nucleotide sequences of Caenorhabditis elegans core histone genes. Genes for different histone classes share common flanking sequence elements

We have determined the nucleotide sequence of core histone genes and flanking regions from two of approximately 11 different genomic histone clusters of the nematode Caenorhabditis elegans. Four histone genes from one cluster (H3, H4, H2B, H2A) and two histone genes from another (H4 and H2A) were analyzed. The predicted amino acid sequences of the two H4 and H2A proteins from the two clusters are identical, whereas the nucleotide sequences of the genes have diverged 9% (H2A) and 12% (H4). Flanking sequences, which are mostly not similar, were compared to identify putative regulatory elements. A conserved sequence of 34 base-pairs is present 19 to 42 nucleotides 3' of the termination codon of all the genes. Within the conserved sequence is a 16-base dyad sequence homologous to the one typically found at the 3' end of histone genes from higher eukaryotes. The C. elegans core histone genes are organized as divergently transcribed pairs of H3-H4 and H2A-H2B and contain 5' conserved sequence elements in the shared spacer regions. One of the sequence elements, 5' CTCCNCCTNCCCACCNCANA 3', is located immediately upstream from the canonical TATA homology of each gene. Another sequence element, 5' CTGCGGGGACACATNT 3', is present in the spacer of each heterotypic pair. These two 5' conserved sequences are not present in the promoter region of histone genes from other organisms, where 5' conserved sequences are usually different for each histone class. They are also not found in non-histone genes of C. elegans. These putative regulatory sequences of C. elegans core histone genes are similar to the regulatory elements of both higher and lower eukaryotes. The coding regions of the genes and the 3' regulatory sequences are similar to those of higher eukaryotes, whereas the presence of common 5' sequence elements upstream from genes of different histone classes is similar to histone promoter elements in yeast.