Biology 2382B Lecture Notes - Lecture 4: Secretion, Membrane Transport Protein, Golgi Apparatus
28 Feb 2019
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Learning objectives: protein-targeting, er: structure and function, contranslational translocation, protein modifications in er, mitochondrial import of proteins. Protein sorting/targeting: typical mammalian cell, 10,000 proteins, must be localized correctly, newly made peptides must be directed to the correct destination, targeting, direct proteins to the right destinations (organelles, during or after synthesis. Sorting: direct proteins to the secretory pathway (er, golgi, lysosomes). Er): those which reside in er and proteins which are sorted to pm, Golgi complex, and lysosomes: accordingly, two major protein-sorting pathways are known: non- secretory and secretory. Basic mechanisms of protein targeting to the membranes of organelles are common: Signal sequence: receptor for the signal sequence. Identify cellular features by microscopy, isolate & homogenize them to free organelles. Sucrose density-gradient centrifugation of homogenate allows for isolation of microsomes & ribosomes. Sds-page is used to identify newly translated proteins. Secretory proteins enter the er lumen: experiment showing that secreted proteins must first go through the er.
