Biology 2382B Lecture : Receptor Mediated Endocytosis.docx
9 Dec 2012
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Phagocytosis - process by which relatively large particles (e. g. , bacterial cells) are internalized by certain eukaryotic cells (i. e. phagoctyes of immune system) in a process that involves extensive remodeling of the actin cytoskeleton. Pinocytosis not specific; it is the internalization of extracellular fluid that could contain a variety of compounds and substances. Receptor-mediated endocytosis - method of selective internalization of specific extracellular molecules (ligands) Ldl (low-density lipoprotein), transferrin, hormones (e. g. insulin), certain glycoproteins, etc. Amphipathic shell - composed of a phospholipid monolayer, apolipoprotein, and cholesterol. Binding of ldl particles to ldlr is ph dependent. Long n-terminal exoplasmic segment with a ligand binding domain and - propeller domain. Normal ph (~7. 0) = the ligand-binding arm binds tightly to apob (which is associated with ldl particle) Propeller domain become protonated and bind with high affinity to the negatively charged residues in the ligand-binding arm. The ph determines how ldlr associated with ldl particle .
