BIOL 2021 Chapter Notes - Chapter 9.1: Hydrolase, Clathrin, Mannose
11 Mar 2018
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Golgi network: pathway that delivers lysosomal hydrolases from tgn to lysosomes, enzymes first delivered to endosomes in transport vesicles bud from tgn before they move to endolysosomes & lysosomes. M6p groups & bind to lysosomal hydrolases on luminal side of membrane & to adaptor proteins in assembling clathrin coats on cytosolic side. After receptor is deliver, hydrolases dissociate from receptor: vesicles are coated with retromer, a coat protein complex specialized for endosome-to-tgn transport, which returns receptors to tgn for reuse. Figure 13-45 transport of newly synthesized lysosomal hydrolases to endosomes. Sequential action of two enzymes in cis & trans golgi network adds m6p groups to precursors of lysosomal enzymes. M6p- tagged hydrolases then segregates from all other types of proteins in tgn b/c adaptor proteins in clathrin coat binds m6p receptors, which bind m6p-modified lysosomal hydrolases. Clathrin coated vesicles bud off from tgn, shed of coat & fuse with early endosomes.
