Na+ Tolerance and Na+ Transport in Higher Plants

Many types of cells methylate phospholipids using two methyltransferase enzymes that are asymmetrically distributed in membranes. As the phospholipids are successively methylated, they are translocated from the inside to the outside of the membrane. When catecholamine neurotransmitters, lectins, immunoglobulins or chemotaxic peptides bind to the cell surface, they stimulate the methyltransferase enzymes and reduce membrane viscosity. The methylation of phospholipids is coupled to Ca2+ influx and the release of arachidonic acid, lysophosphatidylcholine, and prostaglandins. These closely associated biochemical changes facilitate the transmission of many signals through membranes, resulting in the generation of adenosine 3',5'-monophophate in many cell types, release of histamine in mast cells and basophils, mitogenesis in lymphocytes, and chemotaxis in neutrophils.

https://science.sciencemag.org/content/sci/209/4461/1082.full.pdf

Phospholipid methylation and biological signal transmission

Transposable elements are mobile genetic units that exhibit broad diversity in their structure and transposition mechanisms. Transposable elements occupy a large fraction of many eukaryotic genomes and their movement and accumulation represent a major force shaping the genes and genomes of almost all organisms. This review focuses on DNA-mediated or class 2 transposons and emphasizes how this class of elements is distinguished from other types of mobile elements in terms of their structure, amplification dynamics, and genomic effect. We provide an up-to-date outlook on the diversity and taxonomic distribution of all major types of DNA transposons in eukaryotes, including Helitrons and Mavericks. We discuss some of the evolutionary forces that influence their maintenance and diversification in various genomic environments. Finally, we highlight how the distinctive biological features of DNA transposons have contributed to shape genome architecture and led to the emergence of genetic innovations in different eukaryotic lineages.

/pdf/dna-transposons-and-the-evolution-of-eukaryotic-genomes-4rq0mdhrsc.pdf

DNA Transposons and the Evolution of Eukaryotic Genomes

http://auburn.edu/academic/agriculture/fisheries/genomics/FISH7660%202006/DNA%20marker%20review%20paper-Aquaculture.pdf

DNA marker technologies and their applications in aquaculture genetics.

/pdf/the-structure-biosynthesis-and-function-of-glycosylated-4rbegebbn2.pdf

The structure, biosynthesis and function of glycosylated phosphatidylinositols in the parasitic protozoa and higher eukaryotes.

We have identified a novel stress inducible gene, Ehssp1 in Entamoeba histolytica, the causative agent of amebiasis. Ehssp1 belongs to a polymorphic, multigene family and is present on multiple chromosomes. No homologue of this gene was found in the NCBI database. Sequence alignment of the multiple copies, and genomic PCR data restricted the polymorphism to the central region of the gene. This region contains a polypurine stretch that encodes a domain rich in acidic and basic amino acids. Under normal culture conditions only one copy of this multigene family is expressed, as observed by Northern blot and RT-PCR analysis. The size of this copy of the gene is 1,077 nucleotides, encoding a protein of 359 amino acids. The polymorphic domain in this copy is 64 nucleotides long. However, on exposure of cells to stress conditions such as heat shock or oxidative stress, multiple polymorphic copies of the gene are expressed, suggesting a possible role of this gene in adaptation of cells to stress conditions. The gene copy expressed under normal conditions, and the expression profile of cells under heat stress was identical in two different strains of E. histolytica tested. Interestingly, the extent of polymorphism in this gene was very less in E. dispar, a nonpathogenic sibling species of E. histolytica. Ehssp1 was found to be antigenic in invasive amebiasis patients.

/pdf/stress-dependent-expression-of-a-polymorphic-charged-antigen-287piqf9bn.pdf

Stress-Dependent Expression of a Polymorphic, Charged Antigen in the Protozoan Parasite Entamoeba histolytica

Human growth hormone (hGH) and ovine prolactin (oPRL) are both lactogenic as defined by their ability to induce milk-protein synthesis in vitro in the presence of insulin and hydrocortisone. At physiological concentrations, both hGH and oPRL have similar dose-response curves in a mouse mammary gland organ culture system. Binding of 125I-labeled hGH (125I-hGH) to lactogenic receptors is competed by both hGH and oPRL, and the competition curves are nearly superimposable. Moreover, solubilized membrane proteins bound with either 125I-hGH or 125I-labeled oPRL (125I-oPRL) show the same sedimentation pattern on sucrose gradients. However, methylation of membrane phospholipids in the presence of the methyl donor S-adenosyl-L-methionine only increases the binding of 125I-hGH. Binding of either 125I-oPRL or 125I-labeled bovine growth hormone (125I-bGH) was unaffected. Addition of concanavalin A (Con A) to the membranes decreased binding of 125I-oPRL to the lactogenic site by 80%, whereas 125I-hGH binding was decreased by only 40%, with the binding of 125I-bGH unaffected. However, both hGH-and oPRL-bound proteins bind to Con A-Sepharose columns to the same extent. These results suggest that although hGH and oPRL bind to the same lactogenic site with similar affinities and elicit similar biological responses, modification of membranes either by phospholipid methylation or by Con A differentially affects the binding of these two hormones.

Membrane modification differentially affects the binding of the lactogenic hormones human growth hormone and ovine prolactin

A second short repeat sequence detected downstream of rRNA genes in the Entamoeba histolytica rDNA episome.

Identification of novel genes of non-pathogenic Entamoeba dispar by expressed sequence tag analysis.

Lipophosphoglycan has recently been demonstrated on the cell surface of Entamoeba histolytica strain HM-1:IMSS. A monoclonal antibody against this molecule had failed to react with some other strains of E. histolytica, including the strain Rahman. To determine if a structurally distinct lipophosphoglycan existed in Rahman, [ 3 H]galactose-labeled glycoconjugates were electrophoresed through sodium dodecyl sulfate polyacrylamide gel electrophoresis. The electrophoretic pattern in Rahman was very different compared to that obtained with strains HM-1:IMSS and 200:NIH. A number of experiments including sensitivity to mild acid, nitrous acid and phosphoinositol-specific phospholipase C suggest that the Rahman glycoconjugate is indeed a lipophosphogylcan-like molecule but distinctly different from that of HM-1:IMSS. Mild acid-treated glycoconjugates from Rahman and HM-1:IMSS revealed the presence of neutral trisaccharides and monosaccharides in Rahman but not in HM-1:IMSS. Human immune sera from amoebiasis patients and a polyclonal antibody against HM-1:IMSS liphophosphoglycan both recognized Rahman glycoconjugate. Thus, while lipophosphoglycan molecules from the two strains share common epitopes, they are clearly distinct from each other. Molecules bearing resemblance to lipophosphoglycan could not be detected in other Entamoeba species, namely Entamoeba invadens and Entamoeba moshkovskii.

Lipophosphoglycan is present in distinctly different form in different entamoeba histolytica strains and absent in entamoeba moshkovskii and entamoeba invadens

Alok Bhattacharya

Papers

Stress-Dependent Expression of a Polymorphic, Charged Antigen in the Protozoan Parasite Entamoeba histolytica

Membrane modification differentially affects the binding of the lactogenic hormones human growth hormone and ovine prolactin

A second short repeat sequence detected downstream of rRNA genes in the Entamoeba histolytica rDNA episome.

Identification of novel genes of non-pathogenic Entamoeba dispar by expressed sequence tag analysis.

Lipophosphoglycan is present in distinctly different form in different entamoeba histolytica strains and absent in entamoeba moshkovskii and entamoeba invadens