Linear and non-linear regression analysis of genotype X environment interactions in pearl millet

Summary Regression analysis was computed on the grain yield of 15 single cross F₁ hybrids of pearl millet (Pennisetum typhoides (Burm.) S. & H.) evaluated in 20 environments at 19 sites in India to assess the nature of genotype X environment interactions. Linear, quadratic, cubic, twoand three-intersecting straight line models were examined for fit. The interactions of six hybrids viz. MH 110, MH 113, MH 114, MH 115, MH 120 and MBH 110 were explained by the linear regression model. The response of the remaining nine hybrids was largely non-linear. The two and three-intersecting straight line models fit better than the quadratic and cubic models and explained non-linearity of response. The two-intersecting straight line models fit for 6 hybrids MH 106, MH 107, MH 112, MH 116, MH 117 and BJ 104. The response of MH 109 was best explained by a three-intersecting straight line model, but there still existed a significant remainder variation. The truncation of environmental range by assuming moving division points was more efficient than the fixed division points for the segmental regression models. The stability of hybrid varieties on the best fitting model has been discussed.     

Killing of Escherichia coli cells modulated by components of the stability system ParD of plasmid R1

Summary The proteins P10 and P12 have been shown to be gene products of a new stability system, ParD, of plasmid R1. It is now shown that an R1 miniplasmid, pAB112, carrying a trans-complementable amber mutation in the gene of the P10 protein, is lethal for the host in the absence of suppression. This lethal effect is suppressed in a supF background and also by deletions in pAB112 that affect the gene of the P12 protein. These data indicate that the P12 protein has a lethal effect on the host and that this effect is neutralized by the P10 protein. The possibility that the stabilization conferred by the ParD system could be due to a counterselection, mediated by P12, of cells that lose the plasmid at cell division, is discussed.     

Application of a directed conformational search for generating 3-D coordinates for protein structures from alpha-carbon coordinates.

A directed conformational search algorithm using the program CONGEN (ref. 3), which samples backbone conformers, is described. The search technique uses information from the partially built structures to direct the search process and is tested on the problem of generating a full set of backbone Cartesian coordinates given only alpha-carbon coordinates. The method has been tested on six proteins of known structure, varying in size and classification, and was able to generate the original backbone coordinates with RMSs ranging from 0.30-0.87A for the alpha-carbons and 0.5-0.99A RMSs for the backbone atoms. Cis peptide linkages were also correctly identified. The procedure was also applied to two proteins available with only alpha-carbon coordinates in the Brookhaven Protein Data Bank; thioredoxin (SRX) and triacylglycerol acylhydrolase (TGL). All-atom models are proposed for the backbone of both these proteins. In addition, the technique was applied to randomized coordinates of flavodoxin to assess the effects of irregularities in the data on the final RMS. This study represents the first time a deterministic conformational search was used on such a large scale.     

Structural genes of glutamate 1-semialdehyde aminotransferase for porphyrin synthesis in a cyanobacterium and Escherichia coli

Summary In bacteria 5-aminolevulinate, the universal precursor in the biosynthesis of the porphyrin nucleus of hemes, chlorophylls and bilins is synthesised by two different pathways: in non-sulphur purple bacteria (Rhodobacter) or Rhizobium 5-aminolevulinate synthase condenses glycine and succinyl-CoA into 5-aminolevulinate as is the case in mammalian cells and yeast. In cyanobacteria, green and purple sulphur bacteria, as in chloroplasts of higher plants and algae a three step pathway converts glutamate into 5-aminolevulinate. The last step is the conversion of glutamate 1-semialdehyde into 5-aminolevulinate. Using a cDNA clone encoding glutamate 1-semialdehyde aminotransferase from barley, genes for this enzyme were cloned from Synechococcus PCC6301 and Escherichia coli and sequenced. The popC gene of E. coli, previously considered to encode 5-aminolevulinate synthase, appears to be a structural gene for glutamate 1-semialdehyde aminotransferase. Domains with identical amino acid sequences comprise 48% of the primary structure of the barley, cyanobacterial and putative E. coli glutamate 1-semialdehyde aminotransferases. The cyanobacterial and barley enzymes share 72% identical residues. The peptide containing a likely pyridoxamine phosphate binding lysine is conserved in all three protein sequences.     

Immunological identification of yeast SCO1 protein as a component of the inner mitochondrial membrane

Summary The SCO1 gene of Saccharomyces cerevisiae encodes a 30 kDa protein which is specifically required for a post-translational step in the accumulation of subunits 1 and 2 of cytochrome c oxidase (COXI and COXII). Antibodies directed against a -Gal::SCO1 fusion protein detect SCO1 in the mitochondrial fraction of yeast cells. The SCO1 protein is an integral membrane protein as shown by its resistance to alkaline extraction and by its solubilization properties upon treatment with detergents. Based on the results obtained by isopycnic sucrose gradient centrifugation and by digitonin treatment of mitochondria, SCO1 is a component of the inner mitochondrial membrane. Membrane localization is mediated by a stretch of 17 hydrophobic amino acids in the amino-terminal region of the protein. A truncated SCO1 derivative lacking this segment, is no longer bound to the membrane and simultaneously loses its biological function. The observation that membrane localization of SCO1 is affected in mitochondria of a rho ⁰ strain, hints at the possible involvement of mitochondrially coded components in ensuring proper membrane insertion.     

Interleukin-1 inhibits PGE2 binding to macrophage-like P388D1 cells by a cyclic AMP-independent process

The interaction between interleukin IL-1α and PGE₂ on P388D₂ on cells has been investigated. Preincubation of murine macrophage-like cells, P388D₁, with IL-1α (0–73 pM) reduced the binding of PGE₂ to these cells in a concentration-dependent manner. Scatchard analysis showed that IL-1α decreased the PGE₂ binding by lowering both the high and low affinity receptor binding capacities (from 0.31 ± 0.02 to 0.12 ± 0.01 fmol/10⁶ cells for the high affinity receptor binding sites and from 2.41 ± 0.12 to 1.51 ± 0.21 fmol/10⁶ cells for the low affinity receptor binding sites). However, the dissociation constants of the receptor of the IL-1α-treated cells remained unchanged. Inhibition of PGE₂ binding IL-1α did not involve changes in either protein phosphorylation or intracellular cyclic AMP levels. Our data clearly show that IL-1α inhibits the binding of PGE₂ to monocytes/macrophages and may thereby counter the immunosuppressive actions of PGE₂.     

What are mycoplasmas: The relationship of tempo and mode in bacterial evolution

Summary In phenotype the mycoplasmas are very different from ordinary bacteria. However, genotypically (i.e., phylogenetically) they are not. On the basis of ribosomal RNA homologies the mycoplasmas belong with the clostridia, and indeed havespecific clostridial relatives. Mycoplasmas are, however, unlike almost all other bacteria in the evolutionary characteristics of their ribosomal RNAs. These RNAs contain relatively few of the highly conserved oligonucleotide sequences characteristic of normal eubacterial ribosomal RNAs. This is interpreted to be a reflection of an elevated mutation rate in mycoplasma lines of descent. A general consequence of this would be that the variation associated with a mycoplasma population is augmented both in number and kind, which in turn would lead to an unusual evolutionary course, one unique in all respects. Mycoplasmas, then, are actually tachytelic bacteria. The unusual evolutionary characteristics of their ribosomal RNAs are the imprints of their rapid evolution.     

Highly potent and specific inhibitors of human renin

We designed aldehyde derivatives of small peptides representing the C-terminal portion of angiotensin I sequence as an inhibitor of human renin. Among compounds that we synthesized, benzyloxycarbonyl (Z)-Phe-His-Leucinal (compound V), Z-Pro-Phe-His-Leucinal (Compound IV) and Z-[3-(1'-naphthyl)Ala]-His-Leucinal (compound VII) markedly inhibited human renin (IC50, 7.5 X 10(-7), 3.2 X 10(-7) and 8.0 X 10(-8) mol/l, respectively). Compound VII was shown to be noncompetitive (Ki = 2.4 X 10(-7) mol/l). It did not inhibit either cathepsin D or pepsin. Compound V had slight or no inhibitory effect at the concentration of 10(-5) mol/l on six animal renins except for monkey and rabbit renins. Results obtained show that these aldehyde compounds are highly selective and species specific inhibitors for human and monkey renins.     

H1° histones of normal and cancer human cells

Summary H1° histones were purified by preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis from human lung carcinoma (line DMS79), human hepatoblastoma (HepG2), human adult lung and human adult and fetal liver. The purified human H1° histones were analyzed for their amino acid composition and terminal residues. The comparative analysis of the amino acid compositions of the different human H1° histones showed that: (a) all the H1° preparations have the characteristically high lysine content associated with a low arginine content, which distinguishes outer histones from core histones; (b) H1° is distinguishable from other H1 histones by the presence of methionine and histidine; (c) H1° histones from human adult, fetal and cancer cells are very similar in amino acid composition, and in cancer cells the level of the H1° histone is not inversely related with cell growth rate nor with the expression of the -fetoprotein gene.