How does an inhibitor of N-acetylglucosamine phosphotransferase affect lysosomal

Question

How does an inhibitor of N-acetylglucosamine phosphotransferase affect lysosomal protein sorting? As a result of the treatment, lysosomal proteins (1 point) O are secreted from the cell O are retained in the Golgi network. O are retained in the ER. O remain tightly bound to M6P receptors 0 accumulate in the lysosome as non-functional precursor proteins Which of the following modification is most likely to happen on a protein that passes through the cisternae of the Golgi? The protein is as you answer this question, please think about where each of these modifications processes take place! 2. (1 point) modified co-translational with a pre-formed N-glycan "tree" if it contains an Asn - X-Ser/Thr consensus site O folded by BiP O poly-ubiquitinated O interacting with PDI to help it form the correct disulfide bonds modified on its N-glycan in a step-wise fashion through additional and removal of sugars 3. What is the function of the adaptor complex in clathrin mediated transport? (1 point) O 0 It induces membrane curvature It helps pinch off the vesicle O It recruits the cargo to the site of vesicle budding through specific interaction with signals in the cytosolic tail of cargo receptors O It recruits the cargo into the site of vesicle budding through specific interaction with signals in the exoplasmic tail of cargo receptors It induces the uptake of all transmembrane proteins in the plasma membrane 4. Which sorting signal has to be present on a protein in order to be sorted into multi-vesicular bodies? (1 point) O N-terminal hydrophobic sequence O Amphiphatic helix O Stretches of positively charged amino acids O Mono-ubiquitin O poly-ubiquitin

Explanation / Answer

1. In presence of inhibitor of N-acetylglucosamine-phosphotransferase, the lysosomal proteins remain tightly bpund to M6P receptors.

The formation of mannose -6-phosphate residues is catalysed by the sequential action of two enzymes. One of them is N-acetyleglucosamine phosphotransferase. So in presence of its inhibitor, the lysosomal proteins remain tightly bound to M6P receptors.

2. The protein is modified on its N-glycan in a step wise fashion through additional and removal of sugars.

Reason: Pathway of protein sorting in golgi is for selective transport of proteins to lysosomes. Lysosomal proteins are marked by M6P that are formed by modification of their N-linked oligosachharides shortly after entry into golgi.

3. It recruites the cargo into the site of vesicle budding through specific interactions with signals in the exoplasmic tail of cargo receptors.

Clathrin adaptor protein are known as adaptins. These are vesicular transport adaptor proteins associated with clathrin. The association between adaptin and clathrin are important for vesicular cargo selection and transportation. The clathrin associated protein complexes interact with the cytoplasmic tails of membrane proteins and lead to their selection and concentration.

4. Poly-ubiquitin- Because sorting of multivesicular bodies depends on the biosynthetic addition of ubiquitin chain- a chain of ubiquitin molecules attached end to end on a substrate protein to form a poly-ubiquitin.

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