Free ribosomes synthesize the proteins that function in the cytosol, while bound ribosomes make proteins that are distributed by the membrane systems, including those which are secreted from the cell.
AB - During its 48-h asexual life cycle within human erythrocytes, Plasmodium falciparum grows to many times its own size and divides to produce 16-32 new parasites. This rapid multiplication requires active synthesis of new membranes and is fueled by phospholipid precursors and fatty acids that are scavenged from the human host. Plasmodium membrane biogenesis relies heavily on the expression of parasite enzymes that incorporate these precursors into phospholipids. However, little is known about the genes involved in membrane biogenesis or where this process takes place within the parasite. Here, we describe the analysis in P. falciparum of the first step of phospholipid biosynthesis that controls acylation of glycerol 3-phosphate (GPAT) at the sn-1 position. We show that this activity is of parasite origin and is specific for glycerol 3-phosphate substrate. We have identified the gene, PfGAT, encoding this activity in P. falciparum and reconstituted its codon composition for optimal expression in the yeast Saccharomyces cerevisiae. PfGAT complements the lethality of a yeast double mutant gat1Δgat2Δ, lacking GPAT activity. Biochemical analysis revealed that PfGatp is a low affinity GPAT enzyme with a high specificity for C16:0 and C16:1 substrates. PfGatp is an integral membrane protein of the endoplasmic reticulum expressed throughout the intraerythrocytic life cycle of the parasite but induced mainly at the trophozoite stage. This study, which describes the first protozoan GPAT gene, reveals an important role for the endoplasmic reticulum in the initial step of Plasmodium membrane biogenesis.
SYNTHESIS, EVALUATION, MODELING AND …
Figures 10.4 illustrates the movement of the secretory vesicles through the rough and the smooth ER. The smooth ER extends from the RER and serves as a site for lipid biosynthesis for the production of endosomes, lysosomes and plasma membrane as well as for the neurotransmitter vesicles. New membrane protein that begins its synthesis in the RER continues in the SER where pieces of the SER bud off to form transport vesicles that shuttle to the Golgi apparatus with their contents.
Takes place in the mitochondrial matrix.
T1 - The Plasmodium falciparum PfGatp is an Endoplasmic Reticulum Membrane Protein Important for the Initial Step of Malarial Glycerolipid Synthesis
PTM of oxidative folding takes place in the outer membrane
Within the last twenty years it has become apparent that all intracellular membrane trafficking is based on the same fundamental mechanisms. The same operations involved in the synthesis and transport of vesicles at the ER and Golgi apparatus in the soma are employed in a modified fashion during neurosecretion. The major difference is that vesicle trafficking during neurosecretion is regulated by Ca2+ influx whereas vesicle trafficking during the synthesis and transport of vesicles is not. Unregulated trafficking is termed constitutive. In both cases, however, trafficking is made up of a series of steps involving budding of vesicles, their docking with other organelles, and fusion with the membranes of these organelles. These processes are believed to be present during vesicle biogenesis when the ER generates vesicles that fuse with the Golgi apparatus, when the endosomes are trafficked to the lysosomes, and when vesicle membrane is recaptured from the nerve ending plasma membrane. There is a budding from their membrane origin, a movement to the destination point, and finally the docking of the vesicles with the target organelle where it attaches to and fuses with the organelle membrane.
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Chloroplast is a plant subcellular organelle where photosynthesis takes place. Outer membrane of chloroplast is permeable. Inner membrane encloses stroma. Thylakoid is flattened membrane surrounded vesicle. This is the place where light reaction occurs. In stroma, fluid surrounding the thylakoids is the place where the dark reaction occurs. Chlorophylls are the green pigments; they are present in the thylakoid membrane of chloroplast. They absorb deep blue and red light. Secondary light absorbing pigments are called accessory pigments. They are carotenoids and phycobilins. Photosystems are the light absorbing pigments of thylakoid membrane arranged in functional sets.