Primary structure of the ovine pituitary follitropin beta-subunit.

The complete amino acids sequence of the ovine pituitary follitropin beta-subunit was established by studying the tryptic, chymotryptic and thermolytic peptides. The N-terminal sequence of the subunit was confirmed by subjecting the oxidated protein to Edman degradation in an automated sequenator. Automated Edman degradation of the reduced and alkylated (with iodo [14C]acetamide) beta-subunit indicated that most of the molecules used in the sequence studies had lost the N-terminal serine residue. This also confirmed the location of the first five half-cystine residues in the sequence. The proposed structure shows the presence of 111 amino acid residues with the two oligosaccharide moieties linked to asparagine residues located at positions 6 and 23. Heterogeneity occurs at both the termini of the polypeptide chain. Comparison of the sequence of beta-subunit of the ovine hormone with that proposed for human follitropin beta-subunit shows the absence of any deletions in the middle of the peptide chain. Of the 13 replacements, 11 residues can be explained on the basis of a single base change in the codon. The single tryptophan residue of the follitropin occupies an identical position in all the four species that have been studied. The region corresponding to residues 63-105 of the ovine beta-subunit is highly conserved in all the species.     

Is deglycosylated human chorionic gonadotropin an antagonist to human chorionic gonadotropin? Characterization of deglycosylated human chorionic gonadotropin action in two testicular interstitial cell fractions

In order to determine the significance of carbohydrate residues of human chorionic gonadotropin (hCG) in receptor interaction and signal transduction leading to steroidogenesis, the effect of deglycosylated hCG (DG-hCG) was studied in vitro with two different hCG-responsive purified testicular interstitial cell fractions. Fraction I light cells, previously found to bind 125I-labeled hCG with high affinity without producing testosterone, also bound 125I-labeled DG-hCG with high affinity (Kd 7.2.10(-10) M) without stimulating testosterone production. Fraction IV heavier cells, which produced testosterone in response to hCG without detectable high-affinity hCG-binding sites, neither bound DG-hCG nor sufficiently produced cAMP and testosterone in response. With the addition of intact hCG, DG-hCG inhibited cAMP levels, although not sufficiently to inhibit testosterone production. This observation was contrary to previous studies in which DG-hCG was shown to be an antagonist to hCG action. We conclude that: (a) DG-hCG retains its binding activity in light cells and this high-affinity binding is unrelated to steroidogenesis; (b) DG-hCG does not bind to heavier cells with high affinity and loses its biological activity as result of deglycosylation; (c) DG-hCG actions in this study strengthen the concept of two different hCG-responsive cells in the rat interstitium which, if not separated, will yield misleading data supporting the coexistence of hCG high-affinity binding and biological response in the same cell; and (d) DG-hCG partially antagonizes the activation of adenylate cyclase but does not block testosterone production, thus questioning the usefulness of this analogue in antagonizing the action of native hCG in rat testis.     

Influence of carbohydrates on the antigenic structure of gonadotropins: distinction of agonists and antagonists.

The biological properties of glycosylated (native) and deglycosylated gonadotropins are different. The immunological characteristics of antibodies prepared against deglycosylated lutropin and human chorionic gonadotropin were investigated. Distinct antibodies of rabbit polyclonal antisera against deglycosylated lutropin and deglycosylated chorionic gonadotropin were separated by affinity chromatography on divinylsulfonyl-Sepharose-immobilized hormone or antagonist columns, respectively, in successive runs. Antibodies that could discriminate between agonist and antagonistic forms of the hormones could thus be obtained. In radioimmunoassays using 125I-labeled antagonists and respective antagonist antibodies, only the deglycosylated hormones or their deglycosylated alpha-subunits showed preferential reaction. Based on recombinations using different deglycosylated subunits, it was concluded that the loss of antennary sugars in the alpha-subunits was mainly responsible for the changes that led to the formation of antagonist-specific antibodies. Only the agonist-specific antibody could neutralize hormone action. Thus, the type and extent of glycosylation appears to influence the antigenic structure of these secreted glycoproteins.     

Effects of homobrassinolide application on plant metabolism and grain yield under irrigated and moisture-stress conditions of two wheat varieties

Homobrassinolide (BR) was applied either as a seed treatment or foliar spray to two contrasting wheat varieties, viz. C306 (drought tolerant) and HD2329 (drought susceptible), to examine its effects on plant metabolism and grain yield under irrigated and moisture-stress/rainfed conditions. BR application resulted in increased relative water content, nitrate reductase activity, chlorophyll content and photosynthesis under both conditions. BR application also improved membrane stability (lower injury). These beneficial effects resulted in higher leaf area, biomass production, grain yield and yield related parameters in the treated plants. All the treatments were significantly better than the untreated control. Generally, 0.05 ppm either as a seed treatment or foliar spray was more effective than the 0.01 ppm treatment. The drought-tolerant genotype C306 showed more response to BR application under moisture-stress/rainfed condition than HD 2329. Increased water uptake, membrane stability and higher carbon dioxide and nitrogen assimilation rates under stress seemed to be related to homobrassinolide-induced drought tolerance.     

Effect of 5-sulfosalicylic acid on antioxidant activity in relation to vase life of <Emphasis Type="Italic">Gladiolus</Emphasis> cut flowers

An experiment was conducted to study the effect of 5-sulfosalicylic acid (5-SSA) on the vase life of cut flowers of Gladiolus grandiflora variety ‘Green Willow’. The vase solution having 5-SSA significantly increased cumulative uptake of vase solution, vase life, number of opened florets and decreased the number of unopened florets compared to the controls. Spikes kept in vase solution containing 5-SSA also exhibited lower respiration rates, lipid peroxidation and lipoxygenase (LOX) activity, and higher membrane stability, soluble protein concentration, and activity of superoxide dismutase (SOD) and catalase. Results suggest that 5-SSA increases vase life by increasing the reactive oxygen species (ROS) scavenging activity of the Gladiolus cut flowers.     

Insight into Early-Stage Unfolding of GPI-Anchored Human Prion Protein

Prion diseases are fatal neurodegenerative disorders, which are characterized by the accumulation of misfolded prion protein (PrP^Sc) converted from a normal host cellular prion protein (PrP^C). Experimental studies suggest that PrP^C is enriched with α-helical structure, whereas PrP^Sc contains a high proportion of β-sheet. In this study, we report the impact of N-glycosylation and the membrane on the secondary structure stability utilizing extensive microsecond molecular dynamics simulations. Our results reveal that the HB (residues 173 to 194) C-terminal fragment undergoes conformational changes and helix unfolding in the absence of membrane environments because of the competition between protein backbone intramolecular and protein-water intermolecular hydrogen bonds as well as its intrinsic instability originated from the amino acid sequence. This initiation of the unfolding process of PrP^C leads to a subsequent increase in the length of the HB-HC loop (residues 195 to 199) that may trigger larger rigid body motions or further unfolding around this region. Continuous interactions between prion protein and the membrane not only constrain the protein conformation but also decrease the solvent accessibility of the backbone atoms, thereby stabilizing the secondary structure, which is enhanced by N-glycosylation via additional interactions between the N-glycans and the membrane surface.     

Identification and Characterization of NADH Kinase-3 from a Stress-Tolerant Wild Mung Bean Species (Vigna luteola (Jacq.) Benth.) with a Possible Role in Waterlogging Tolerance

Plant Molecular Biology Reporter - In plants, reactive oxygen species accumulate to a toxic level under various abiotic stresses. Many antioxidant defense systems require NADPH as a principal...     

Human pituitary thyrotropin: primary structure of the hormone specific beta subunit

The primary structure of the hormone specific β subunit of human pituitary thyrotropin has been deduced from the composition and complete or partial amino acid sequences of the tryptic and chymotryptic peptides. It consists of 112 amino acid residues with the single oligosaccharide moiety which is assumed to be linked to the asparagine residue at position 23.