Functional characterization of the alveolins, a family of cytoskeleton proteins of malaria parasites.

Malaria remains one of the most serious infectious parasitic diseases in humans. A shared cellular feature of the motile and invasive stages (zoites) of malaria parasites is the presence of a unique cortical cytoskeletal structure named the subpellicular network (SPN), which forms an internal cytoskeletal basket providing mechanical strength to the cell. Malaria parasites have three distinct zoite stages: the merozoite (blood stage); the ookinete (early mosquito stage); and the sporozoite (late mosquito and liver stage). A family of intermediate filament proteins, named alveolins, comprise main building blocks of the SPN. Several Plasmodium alveolins have been shown to be differentially expressed across zoite stages, and to have functionally equivalent and essential roles involved in parasite morphogenesis, tensile strength, motility and infectivity. In this thesis, genetically altered parasite lines expressing disrupted, fluorescent protein-tagged or mutated alveolins were generated in the mouse malaria model P. berghei, to further characterize select alveolin family members with respect to their life stage expression, subcellular localization and trafficking, and their contribution to parasite development, infectivity and mosquito transmission. Through structure-function analysis, the contributions of conserved cysteine motifs to alveolin function and post-translational lipid modification (palmitoylation) were also investigated. Re-examination of the alveolin repertoire identified 13 alveolin family members whose conserved 'alveolin' domains possess tandem repeats of typically 12 amino acids. The results show two alveolins, IMC1c and IMC1e, to be expressed in all three zoite stages and to be essential for blood stage parasite development. Moreover, IMC1c and IMC1e display different temporal recruitment to the SPN. By contrast, the alveolin IMC1d is expressed only in ookinetes and is functionally dispensable. We show that the cysteine motif in the alveolin IMC1c is the site of S-palmitoylation, but is functionally redundant. By contast, the cysteine motifs of IMC1a are important for sporozoite development and infectivity. The combined results suggest that while alveolins have a shared core architecture and overall cytoskeletal function, differences in life stage expression, protein expression level, recruitment to the SPN, and palmitoylation status ensure that each family member makes a unique contribution to parasite development

Palmitoylation of Plasmodium alveolins promotes cytoskeletal function.

S-palmitoylation is a post-translational lipid modification that is widespread among Plasmodium proteins and essential for parasite development. Little is known about the contribution of palmitoylation to the function of individual parasite molecules and structures. Alveolins are major components of the subpellicular network (SPN), a cortical cytoskeleton primarily involved in providing mechanical strength to the cell. We show here that the alveolin IMC1c is palmitoylated on a conserved cysteine motif, and that non-palmitoylated IMC1c displays normal expression, stability and trafficking. However, mutant parasites exhibit reduced osmotic stress resistance and tensile strength. These findings support the hypothesis that alveolin palmitoylation enhances cytoskeletal function by strengthening the connection between the SPN and the adjoining inner membrane complex via lipid anchoring

The Plasmodium alveolin IMC1a is stabilised by its terminal cysteine motifs and facilitates sporozoite morphogenesis and infectivity in a dose-dependent manner.

Apicomplexan parasites possess a unique cortical cytoskeleton structure composed of intermediate filaments. Its building blocks are provided by a conserved family of proteins named alveolins. The core alveolin structure is made up of tandem repeat sequences, thought to be responsible for the filamentous properties of these proteins. A subset of alveolins also possess conserved motifs composed of three closely spaced cysteine residues situated near the ends of the polypeptides. The roles of these cysteine motifs and their contribution to alveolin function remains poorly understood. The sporozoite-expressed IMC1a is unique within the Plasmodium alveolin family in having conserved cysteine motifs at both termini. Using transgenic Plasmodium berghei parasites, we show in this structure-function analysis that mutagenesis of the amino- or carboxy-terminal cysteine motif causes marked reductions in IMC1a protein levels in the parasite, which are accompanied by partial losses of sporozoite shape and infectivity. Our findings give new insight into alveolin function, identifying a dose-dependent effect of alveolin depletion on sporozoite size and infectivity, and vital roles of the terminal cysteine motifs in maintaining alveolin stability in the parasite

Effect of Reaction Pressure and Carrier Gas on Toluene Disproportionation over Molybdenum-ZSM-5 Catalyst.

This study was aimed at evaluating the effects of reaction pressure and temp. on toluene disproportionation using a ZSM-5-based catalyst impregnated with molybdenum. The results of the study showed that both toluene conversion and xylene selectivity were strongly dependent on temp., pressure, and the kind of carrier gas used. Toluene conversion compared at the same temp. and pressure is higher when nitrogen instead of hydrogen was used as the carrier gas. For both carrier gases, toluene conversion increased with both pressure and temp. Also, catalyst deactivation was more rapid and more severe with nitrogen as the carrier gas than with hydrogen

Effect of Reaction Pressure and Carrier Gas on Toluene Disproportionation over Molybdenum-ZSM-5 Catalyst.

This study was aimed at evaluating the effects of reaction pressure and temp. on toluene disproportionation using a ZSM-5-based catalyst impregnated with molybdenum. The results of the study showed that both toluene conversion and xylene selectivity were strongly dependent on temp., pressure, and the kind of carrier gas used. Toluene conversion compared at the same temp. and pressure is higher when nitrogen instead of hydrogen was used as the carrier gas. For both carrier gases, toluene conversion increased with both pressure and temp. Also, catalyst deactivation was more rapid and more severe with nitrogen as the carrier gas than with hydrogen

1,2,4-Trimethylbenzene Transformation Reaction Compared With Its Transalkylation Reaction With Toluene Over USY Zeolite

1,2,4-Trimethylbenzene (TMB) transalkylation with toluene has been studied over USY zeolite type catalyst using a riser simulator that mimics the operation of a fluidized-bed reactor. Reaction mixtures of 50:50 wt % TMB and toluene were used for the transalkylation reaction. The range of temperature investigated was 400-500 degrees C with time on stream ranging from 3 to 15 s. The effect of reaction conditions on the variation of the p-xylene to o-xylene product ratio (P/O), distribution of trimethylbenzene (TMB) isomers (1,3,5-TMB to 1,2,3-TMB), and values of xylene/tetramethylbenzene (X/TeMB) ratios are reported. Comparisons are made between the results of the transalkylation reaction with the results of pure 1,2,4- TMB and toluene reactions earlier reported. Toluene, which was found almost inactive, became reactive upon blending with 1,2,4-TMB. This shows that toluene would rather accept a methyl group to transform to xylene than lose a methyl group to form benzene under the present experimental conditions. The experimental results were modeled using a quasi-steady-state approximation. Kinetic parameters for the 1,2,4-TMB disappearance during the transalkylation reaction and in its conversion into isomerization and disproportionation products were calculated using the catalyst activity decay function based on time on stream (TOS). The apparent activation energies were found to decrease as follows: E-transalkylation > E-isomerization > E-disproportionation

ANTAGONISTIC EFFECT OF MUSK ON ORGANISMS DIFFERENT TYPES

Objective: This study aims to The research aimed at a comparative study the effect of natural and synthetic musk compared to creams that have an anti-fungal and anti-bacterial effect on the growth of Candida albicans that causes vaginal diseases in women, as well as the growth of the bacteria strains include Staphylococcus aureus, Bacillus subtilis, which would be more effective in inhibiting the growth of these microbes and Achieve the recommendation of the Prophet Muhammad for women to treat the vagina with natural musk, find alternatives to synthetic antibiotics, and reduce their negative effects on human health. Methods: This study investigates the antagonistic effect of Anti fungal and bacterial Cream and different natural type {Musk (N. M), Black Musk (B. M)} and chemical Musk {white Musk (W. M), cream Musk (M. C) } on some microorganisms. The types of yeast Candida albicans HVS and the bacteria strains include Staphylococcus aureus, Bacillus subtilis, were tested by means of disk diffusion, Results: Results indicated that Musk has inhibitory effects on the growth of study microorganisms Musk contains active substances similar to antibiotic, alkaloids and volatile oils present in them as they have the ability to stop the growth of many microorganisms. The effect of natural musk was higher than the effect synthetic musk, And the microbes were the most sensitive to musk is Bacillus subtilis. As for anti-microbial creams, the effect of the anti-bacterial cream was more effective in their suppression compared to all kinds of musk unlike the anti-fungal cream which gave a negative result. Conclusion: This study showed that the different concentrations of natural musk have an effective role in inhibiting some of the microbes of this vaginal pathogen, and it has given a positive opposite result to these microbes, and therefore it can be used as a natural antibiotic that reduces side effects on females and the environment