Plasmodium falciparum protein associated with the invasion junction contains a conserved oxidoreductase domain

The merozoite cap protein-1 (MCP-1) of Plasmodium falciparum follows the distribution of the moving Junction during invasion of erythrocytes. We have cloned the gene encoding this protein from a cDNA library using a monoclonal antibody. The protein lacks a signal sequence and has no predicted trans-membrane domains; none of the antisera reacts with the surfaces of intact merozoites, indicating that the cap distribution is submembranous. MCP-1 is divided into three domains. The N-terminal domain includes a 52-amino-acid region that is highly conserved in a large family of bacterial and eukaryotic proteins. Based on the known functions of two proteins of this family and the pattern of amino acid conservation, it is predicted that this domain may possess oxido-reductase activity, since the active cysteine residue of this domain is invariant in all proteins of the family. The other two domains of MCP-1 are not found in any other members of this protein family and may reflect the specific function of MCP-1 in invasion. The middle domain is negatively charged and enriched in glutamate; the C-terminal domain is positively charged and enriched in lysine. By virtue of its positive charge, the C-terminal domain resembles domains in some cytoskeleton-associated proteins and may mediate the interaction of MCP-1 with cytoskeleton in Plasmodium.     

Identification of Frankia Strains by Two-Dimensional Polyacrylamide Gel Electrophoresis

Fifteen Frankia strains from five different plant species were analyzed by two-dimensional polyacryl-amide gel electrophoresis to determine their relatedness by comparing the polypeptide patterns obtained. Three major subgroups (A, C, and D) were found in the Alnus-Comptonia-Myrica cross-inoculation group. An isolate from Purshia tridentata had a unique protein pattern and represents a distinct group of frankiae. Members of group A were isolated from root nodules of Alnus incana subsp. rugosa and Alnus viridis subsp. crispa. Group C organisms were from A. incana subsp. rugosa and Comptonia peregrina nodules, and group D organisms were from A. incana subsp. rugosa, A. viridis subsp. cripsa, and Myrica pensylvanica root nodules. Isolates from each gel group were obtained at several widely separated geographical locations. The results indicate that two-dimensional polyacrylamide gel electrophoresis is useful for identifying Frankia isolates.     

Japanese Hollies: Intolerant Hosts of Meloidogyne arenaria in Microplots

Japanese hollies were itttolerant of Meloidogyne arenaria in field microplot experiments. Ilex crenata var. rotundifolia was relatively more tolerant than I. crenata var. convexa or I. crenata var. helleri. When M. arenaria was added at various itfitial population densities to soil containing plants of "Helleri," "Convexa," and "Rotundifolia," respectively, 91, 75, and 25% were killed by the end of the third growing season. No control plants died during the same period. Initial numbers of M. arenaria larvae and eggs were the only population densities that were correlated (negatively), regardless of cultivar, with plant growth over the three growing seasons. A linear relation was found for initial density of M. arenaria and growth of I. crenata rotundifolia. Increasing nematode density by 10-fold suppressed the growth of this cultivar by 23%.     

Fractionation of primary amyloid fibrils. Characterization and chemical interaction of the subunits.

Amyloid fibrils of kappa origin from a patient with primary amyloidosis are dissociated in various denaturants and fractionated into their subunit components on Sepharose 6B. Solubilization of the fibrils in 4 M guanidine-HCl followed by reduction and alkylation produced 22 000 and 17 000 dalton fractions. Without prior reduction and alkylation, these fractions exist as a high molecular weight protein which can be separated on Sepharose 6B. A high molecular weight protein can be directly dissociated from the amyloid fibril with 1% sodium dodecyl sulfate or 1 M NaCl. Reduction and alkylation of this material produces the two lower molecular weight fractions, i.e., 22 000 and 17 000. These have in the first 20 residues identical N-terminal amino acid sequences; they share immunologic identity and have similar tryptic peptide map profiles. Amino acid analysis of the 22 000 dalton fraction is identical with the intact immunoglobulin light chain isolated from the patient's serum. These data suggest that the insoluble amyloid fibril is the result of aggregation by disulfide linkages between the 22 000 and 17 000 dalton fractions.     

13C NMR spectroscopy of Pyrrolizidine alkaloids

The ¹³C NMR spectra of nine pyrrolizidine alkaloids of the macrocyclic diester type, seven of the corresponding N-oxides and of the parent base retronecine have been recorded and the signals assigned. The 13C NMR signals were found to be sensitive to structural variation in both the diester moiety and the heterocyclic ring system, providing useful information for structural elucidation, particularly when the ¹H NMR spectra may be difficult to interpret.     

Chemical enthalpy-entropy compensation effect in the hydrolysis of p-nitrophenyl carboxylates catalyzed by alkaline mesentericopeptidase

The temperature dependence of the hydrolysis of p-nitrophenyl carboxylates with general formula H(CH₂)_nCOOC₆H₄NO₂ catalyzed by alkaline mesentericopeptidase has been studied (n varying from 1 to 7, temperature range 2–30°C, pH 8.80, 5 vol% dimethylsulfoxide). The activation parameters of the deacylation step depend on the length of the hydrophobic side chain of the substrate molecule ( , , and decrease by 2.0 kcal/mol, 4.9 kcal/mol, and 10 eu, respectively, as the length of the acyl carbon chain increases from n = 1 to n = 4). The following criteria were applied to establish a chemical enthalpy-entropy compensation effect: (a) Exner's plot of log vs : (b) Petersen's plot of log, k/T vs 1/T; (c) Exner's statistical treatment in coordinates log k vs 1/T; (d) according to Krug et al. (ΔH^≠ vs ΔG_Thm^≠). By use of all the above-mentioned criteria the existence of a chemical enthalpy-entropy compensation effect was proved with an isokinetic temperature β of about 470°K, which is significantly higher than the average experimental temperature.     

A Thick-Walled Organism Isolated from the Cockroach Gut by Using a Spent Medium Technique

By using a conditioning technique whereby complex media are inoculated several times with bacteria from the hindgut of the cockroach Eublaberus posticus, a succession of bacterial types occurred. An obligately anaerobic, pleomorphic, thick-walled, gram-positive organism is described which was isolated by this culturing technique.