MCB 2210 FALL 2015 PROBLEM SET 4 1 If a nuclear localization signal were added to the gene encoding a plasma membrane protein where would the protein likely be found a Nucleus b Plasma membrane c Cytoplasm d Lysosomes e Secreted from the cell 2 What does UGGT do if it binds to a misfolded glycoprotein a It interacts with Calnexin and ERp57 and transports the protein to the proteasome b It adds a single mannose back to one of the glucose residues at the exposed end of the recently trimmed oligosaccharide c It adds a single glucose back to one end of the recently trimmed oligosaccharide d It degrades the protein e a and b are correct 3 What are the differences between ribosomes that make secretory proteins and those that make proteins intended for the cytosol a The ribosomes that make secretory proteins are smaller b The ribosomes that make cytosolic proteins are larger c There are no differences between them d The ribosomes that make secretory proteins are denser e a and b are correct 4 How are proteins imported into mitochondria and chloroplasts a Pre translationally b Imported fully formed and properly folded across membrane of the appropriate organelle c Post translationally d Post transcriptionally e b and c are correct 5 The N terminal targeting sequence of mitochondrial matrix proteins is ultimately removed by a a chaperone b a mitochondrial processing glycosidase c mitochondrial processing lipase d mitochondrial signal peptidase e mitochondrial ATP synthase 6 How do the signal sequences of mitochondrial proteins destined for the inner mitochondrial membrane differ from those destined for the mitochondrial matrix a Inner mitochondrial membrane protein signals are all made of alanine b Inner mitochondrial membrane protein signals remain as part of the molecule c Inner mitochondrial membrane protein signals are internal rather than on the end d b and c e Inner mitochondrial membrane protein signals contain adenine 7 Which are functions that molecular chaperones perform to help proteins enter mitochondria a they keep polypeptides unfolded in the cytoplasm b they help pull polypeptides into the mitochondrial matrix c they help fold mitochondrial proteins once they reach the matrix d they direct mitochondrial proteins to the outer mitochondrial membrane e a b and c 8 The outer mitochondrial membrane contains a protein import complex the that includes a n and a protein lined a TOM complex receptor that recognizes and binds mitochondrial proteins channel b TIM complex receptor that recognizes and binds mitochondrial proteins channel c TOM complex receptor that recognizes and binds the outer mitochondrial membrane channel d TIM complex receptor that recognizes and binds the outer mitochondrial membrane channel e importer receptor that recognizes and binds mitochondrial proteins channel 9 Which helps power the movement of the mitochondrial targeting signal on a mitochondrial protein into the mitochondrial matrix a electric potential across the inner mitochondrial membrane acting on the positively charged targeting signal b electric potential across the outer mitochondrial membrane acting on the positively charged targeting signal c ATP d GTP e electric potential across the inner mitochondrial membrane acting on the negatively charged targeting signal 10 Put the following in the correct order I Protein is imported through the TIM complex II Protein is imported through the TOM complex III Fully folded mature protein is located in the mitochondrial matrix IV Protein is folded by mitochondrial chaperone using ATP V Import signal is recognized by receptor protein a V I II IV III b II V III I IV c II III V IV I d V II I IV III e none of the above is correct 11 Proteins that are destined for the thylakoid membrane or the thylakoid lumen must have a a thylakoid targeting domain b a thylakoid lumen domain c a transit peptide d a stroma targeting domain e a and d 12 Compared to mitochondria chloroplasts have an extra membrane enclosed compartment called a Thylakoid b Lumen c Cytoplasm d Stroma e Nucleus 13 If you took a gene that is normally present in the mitochondrial genome and codes for an enzyme that works in the matrix and then inserted the gene into the nucleus of a cell what would you expect the final destination of the protein to be a ER lumen b Nucleus c Secreted d Mitochondrial matrix e None of the above 14 If you took a gene for a protein which is normally found in the cytoplasm and added a mitochondrial targeting signal N terminal amphipathic helix to it and expressed the gene in the cell where would you expect the protein to end up a ER lumen b Nucleus c Cytoplasm d Secreted e Mitochondrial matrix 15 If you engineered a nuclear encoded gene for a mitochondrial matrix protein to contain an Asn X Ser glycosylation signal and a c terminal peroxisomal targeting signal and then inserted the gene into the nucleus of a cell and examined the expressed protein the protein could a Be glycosylated and found in the mitochondrial matrix b Be unglycosylated and in the cytoplasm c Be unglycosylated and exported from the cell d Be unglycosylated and found in the mitochondrial matrix e Be glycosylated and found in the peroxisome 16 If a patient has a lysosomal storage disease in which all lysosomal proteins are found secreted from the cell and those proteins have no Man 6 phosphate attached to their oligosaccharides then the defect is most likely a In the SRP receptor b In the enzyme that adds man 6 p to lysosomal proteins c In the man 6 p receptor d In the lysosomal enzyme RNAase e In the enzyme that co translationally glycosylates proteins 17 In a cell which lacks the mannose 6 phosphate receptor for lysosomal enzymes a The lysosomal enzymes would not be glycosylated and would be secreted from the cell b The lysosomal enzymes would be glycosylated lack mannose 6 phosphate and be secreted from the cell c All glycoproteins would have mannose 6 phosphate d The lysosomal enzymes would be glycosylated have mannose 6 phosphate and be secreted from the cell e None of the above 18 Which is FALSE In order to target a protein to the lysosomes the protein needs to a Be made on ribosomes of the rough endoplasmic reticulum b Have a net positive charge c Have an Asn X Ser glycosylation sequence d Be maintained in an unfolded state by chaperones until it reaches the lysosome e b and d are false 19 If a mitochondrial localization signal were added to a lysosomal protein so that the ER targeting signal