CBIO 3400 Week 5 Study Questions 1 What are SRP and SR Describe their structures and functions regarding protein transportation SRP is a signal recognition particle made up of RNA 300 bp and 6 proteins it is a ribonucleoprotein particle SRP binds the signal sequence pausing translation SR is the SRP receptor It is a heterodimer made up of SR a transmembrane protein 300 AAs and SR a peripheral membrane protein 640 AAs both of these proteins are GTPases The cytoplasmic domain of SR binds SRP OR ribosome and relieves the block in chain elongation i e the paused translation caused by SRP binding the block signal sequence Basically once SR binds SRP translation can start up again 2 There are four different peptide sequences as shown below Describe their sub cellular localization shortly after being synthesized 1 ER lumen b c of SS 2 NH3 localization in ER lumen b c of SS and COO in cytoplasm b c of STA this is a type 1 3 NH3 in cytoplasm b c comes before the SA and COO in ER lumen b c comes before the SA charges always face side that s in cytosol 4 NH3 in ER lumen and COO also in ER lumen b c there s an even of topogenic sequences meaning NH3 case when there s an odd of topogenic sequences and COO are in same compartment instead of distinct compartments as is the 1 3 Proteins are glycosylated in the ER lumen Describe the complete mechanism regarding sugar DATA CBIO3400 chain synthesis transfer and trimming in the ER The glycosylation of a protein is the covalent addition of carbohydrates to the protein If this is N cid 882 linked cid 3 glycosylation cid 3 in cid 3 the cid 3 ER done onto serine or threonine it is called O linked if it is done onto asparagine it is called cid 882 synthesis cid 3 of cid 3 carbohydrate cid 3 chain cid 3 using cid 3 dolichol cid 882 P cid 3 and cid 3 activated cid 3 sugars N linked The steps of N linked glycosylation in the ER are 1 synthesis of carbohydrate chain cid 882 transfer cid 3 of cid 3 carbohydrate cid 3 chain cid 3 to cid 3 asparagine cid 3 of cid 3 protein cid 3 in cid 3 ER using dolichol P and activated sugars 2 transfer of carbohydrate chain to asparagine of protein cid 882 processing cid 3 of cid 3 sugar cid 3 chain cid 3 ER cid 3 and cid 3 Golgi in the ER and 3 processing of sugar chain ER and Golgi UDP cid 3 cid 882 Uridine cid 882 DP CBIO3400 N cid 882 linked cid 3 glycosylation cid 3 in cid 3 the cid 3 ER cid 882 synthesis cid 3 of cid 3 carbohydrate cid 3 chain cid 3 using cid 3 dolichol cid 882 P cid 3 and cid 3 activated cid 3 sugars cid 882 transfer cid 3 of cid 3 carbohydrate cid 3 chain cid 3 to cid 3 asparagine cid 3 of cid 3 protein cid 3 in cid 3 ER cid 882 processing cid 3 of cid 3 sugar cid 3 chain cid 3 ER cid 3 and cid 3 Golgi 14 cid 3 sugar cid 3 residue cid 3 precursor cid 3 Glc 3 Man 9 GlcNAc 2 conserved cid 3 in cid 3 eukaryotes cid 3 modified cid 3 5 cid 882 residue cid 3 core cid 3 remains 3 cid 3 distinct cid 3 glycosidases remove cid 3 glucose Sugars cid 3 are cid 3 bulky cid 3 they cid 3 prevent cid 3 unwanted cid 3 hydrophobic cid 3 interactions cid 3 and cid 3 protein cid 3 aggregation At cid 3 specialized cid 3 ER cid 3 exit cid 3 sites 2 4 What mechanism does the ER utilize to tell whether or not a protein is ready to be delivered to the Golgi 5 ARF1 plays an important role in intracellular vesicle transport Describe the structure function and regulation of ARF1 ARF1 indirectly changes membrane lipid composition via effectors It activates PC specific phospholipase D and also increases phosphatidic acid in the microenvironment ARF1 is regulated by GEF and GAP ARF GDP is present in the cytoplasm and is turned into ARF GTP by GEF ARF GTP is membrane bound and is turned off by GAP 3
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