Plant growth and development are regulated by Internal Signals and by External Environmental Conditions. One important regulator that coordinates growth and development with responses to the environment is the Sesquiterpenoid hormone ABA (Abscisic Acid). ABA plays important roles in many cellular processes including Seed Development, Dormancy, Germination, Vegetative Growth, Leaf Senescence, Stomatal Closure, and Environmental Stress Responses.  ABA is synthesized in almost all cells, but its transport from roots to shoots and the recirculation of ABA in both Xylem and Phloem are important aspects of its physiological role. The most extensively investigated developmental and physiological effects of ABA are those involved in Seed Maturation and Dormancy and in the[..]

Methylococcus capsulatus is an obligate, Gram-negative methanotroph. It generally use the greenhouse gas Methane as a sole carbon and energy source for growth, thus playing major roles in global carbon cycles, and in particular, substantially reducing emissions of biologically generated Methane to the atmosphere. Methylococcus capsulatus is the first complete genome sequence reported from an obligate methanotroph. Genome analysis suggests the ability of M. capsulatus to scavenge copper (including a previously unreported nonribosomal peptide synthetase) and to use copper in regulation of methanotrophy, but the exact regulatory mechanisms remain unclear. The existence of previously unsuspected metabolic flexibility in M. capsulatus, including an ability to grow on[..]

Eukaryotic cells are characterized by extensive subcellular compartmentation whose structural basis is the existence of a number of highly specialized membrane-bound organelles. Each of these organelles is equipped with a specific subset of proteins allowing them to fulfill specific tasks in cellular metabolism. Mitochondria are present in virtually all eukaryotic cells. Mitochondria are the compartments responsible for respiration and oxidative phosphorlyation. They are made up of two highly specialized membrane systems, the OM (Outer Membrane) and IM (Inner Membrane), and two aqueous compartments, the Matrix and the IMS (Intermembrane Space). More than 90% of the mitochondrial proteins are encoded on the nuclear DNA and then synthesized as precursors on cytosolic[..]

The Hh (Hedgehog) proteins are evolutionarily conserved signaling molecules that control the normal growth and patterning of diverse animals including Drosophila and humans. In flies, Hh is required for multiple developmental processes such as embryonic segment patterning, eye and appendage development. A single Drosophila Hedgehog gene has three mammalian counterparts:  SHh  (Sonic Hedgehog),  IHh  (Indian Hedgehog), and  DHh  (Desert Hedgehog). The Hh proteins are extracellular signaling molecules involved in embryonic patterning and organogenesis (Ref.1 & 2). In Drosophila, Hh activates the  Smo  (Smoothened) G-protein-coupled receptor signal transduction pathway through its reaction with the Ptc (Patched) receptor.[..]

Presenilins are polytopic transmembrane proteins, mutations in which are associated with the occurrence of Early-onset familial Alzheimer's disease, a rare form of the disease that results from a single-gene mutation. The physiological functions of Presenilins are unknown, but they may be related to Developmental signaling, Apoptotic signal transduction, or processing of selected proteins, such as the Beta-APP (Beta-Amyloid precursor protein). Presenilin homologues identified in species that do not have an Alzhemier's disease suggests that they may have functions unrelated to the disease, homologues having been identified in Mouse, Drosophila melanogaster, Caenorhabditis elegans and other members of the eukarya including Plants. In humans, there are two known[..]

G-proteins are heterotrimers, consisting of Alpha, Beta and Gamma subunits, and are involved in signaling to distinct effectors. Heterotrimeric G-proteins convey extracellular signals that activate 7-transmembrane-spanning GPCRs (G-Protein-Coupled Receptors) to the inside of cells, communicating this information to effector proteins and thus initiating changes in cell behaviour. GPCRs constitute a large and diverse family of proteins whose primary function is to transduce extracellular stimuli into intracellular signals. GPCRs recognize a variety of ligands and stimuli including Peptide and non-peptide Hormones and Neurotransmitters, Chemokines, Prostanoids and Proteinases, Biogenic amines, Nucleosides, Lipids, Growth factors, Odorant molecules and Light. GPCRs turn on[..]

PKA (Protein Kinase-A) is an enzyme that regulates processes as diverse as growth, development, memory, and metabolism. In its inactivated state, PKA exists as a tetrameric complex of two Catalytic subunits (PKA-C) and a Regulatory (PKA-R) subunit dimer. To date, four regulatory subunits have been identified (RI-Alpha, RI-Beta, RII-Alpha and RII-Beta), which are differentially distributed in mammalian tissues. RI-Alpha and RII-Alpha are expressed ubiquitously, RI-Beta is expressed predominantly in the brain and RII-Beta is expressed primarily in brain, adrenal and adipose tissues. These R subunits define Types-I and II PKA, with both types of holoenzyme having three potential C subunits (Alpha, Beta and Gamma). The C-Alpha and Beta subunits share 93% homology and[..]

GPCR (G-Protein-Coupled Receptors) constitute a large and diverse family of proteins whose primary function is to transduce extracellular stimuli into intracellular signals. They are among the largest and most diverse protein families in mammalian genomes. Also termed Serpentine receptors, GPCRs are polytopic membrane proteins that share a common structure with seven transmembrane segments, but sequence similarity is minimal among the most distant GPCRs. GPCRs recognize a variety of ligands and stimuli including Peptide and non-peptide Hormones and Neurotransmitters, Chemokines, Prostanoids and Proteinases, Biogenic amines, Nucleosides, Lipids, Growth factors, Odorant molecules and Light. These receptors affect the generation of small molecules that act as[..]

The bacterium D. radiodurans (Deinococcus radiodurans) is a Gram-positive, red-pigmented, non-motile bacterium that shows remarkable resistance to a range of damage caused by ionizing radiation, desiccation, UV radiation, oxidizing agents, and electrophilic mutagens. D. radiodurans is best known for its extreme resistance to ionizing radiation; not only can it grow continuously in the presence of chronic radiation, but also it can survive acute exposures to Gamma radiation without dying or undergoing induced mutation (Ref.1 & 2). These amino acid metabolisms also provide metabolites essential for the formation of complex outer membrane lipids and a thick peptidoglycan layer that serves to protect D. radiodurans from lethal doses of radiation. Glycine is basically[..]

Auxin is a classic Phytohormone involved in a myriad of Developmental and Environmental Processes like Embryo Patterning, Cell Division and Elongation, Vascular Differentiation, Lateral Root Initiation, Gravitropism, and Phototropism. IAA (Indole-3-Acetic Acid) is recognized as the key Auxin in most plants with over 20 members of IAA gene family has been recognized in Arabidopsis.  IAA physiologically exists as free acid but IAA can also be found in different conjugated forms, including Ester-types with the Carboxyl group linked via Oxygen to a Sugar (for example Glucose) and Amide-types with the Carboxyl group forming an Amide (Peptide bond) to Amino Acids or Polypeptides. Plants use several pathways to synthesize IAA but none of the pathways is yet defined to[..]

Cholesterol is an important component of cell membrane, and a precursor of Steroid hormones, vitamin D3, and Biliairy Acids. Cell Cholesterol homeostasis is under the control of endogenous Cholesterol synthesis, Cholesterol secretion, and of Lipoprotein Receptor activities that enrich the cell in Cholesterol. Lipoprotein Receptors play an important role in Lipoprotein metabolism and in Cellular Cholesterol homeostasis. LDLs (Low Density Lipoproteins) are the major carriers of Cholesterol as CE (Cholesteryl Esters) in humans. Elevated LDL Cholesterol (>130-160 mg/dl) is one of the major risk factors for CHD (Coronary Heart Disease). For every 1% increase in LDL-Cholesterol, the risk for CHD is increased by 1%-2%. Furthermore, reduction of LDL-Cholesterol[..]

Retinoic Acid, the active form of Vitamin-A (all-trans-Retinol), is a lipophilic molecule, and is known to affect gene transcription. Retinoic Acid is made available in the body through dietary intake and subsequent metabolism in the liver. Vitamin-A is secreted from its storage pools and circulates in blood. In the liver Vitamin-A is converted to all-trans-Retinoic acid, the Carboxylic Acid form of Vitamin-A and diffuses easily to the target tissues through cellular membranes; gets bound to CRABP (Cellular Retinoic Acid Binding Protein) and produces its biological effects through the activation of RARs (Retinoic Acid Receptors). Although biologically active ligands for the RARs also include 9-cis-Retinoic Acid among others, yet circulating levels of 9-cis-Retinoic[..]