There had been a long-standing controversy between two different hypotheses abou

Question

There had been a long-standing controversy between two different hypotheses about the trafficking of proteins through the Golgi that was resolved in a set of experiments that you studied this semester. A) What were the two hypotheses? B) Briefly describe the critical experiments that solved this controversy making clear which hypothesis was confirmed. C) What experimental evidence would have confirmed the other hypothesis? D) Given that the experiments you studied were done in unicellular yeast, which hypothesis would you favor for mammalian cells?

Explanation / Answer

61)

A) The two hypotheses that describe the trafficking of proteins through golgi apparatus are

B) Alberto Luini conducted an experiment using cultured mammalian cells to investigate how large protein complexes moved through the Golgi. Luini observed procollagen only within Golgi cisternae, and never within the vesicles, which are smaller than procollagen. In another experiment conducted by Michael Melkonian, different species of algae export both very large (1.5–2 mm) and more moderately sized (~40 nm) scales which were consistently found within the cisternae, but not in the transport vesicles. The results from these diverse cell types support the cisternal maturation model of protein transport through the Golgi.

C) Vesicular transport model was described by Rothman. Rothman's experiment found that the Golgi cisternae are stable compartments that house certain protein modification enzymes which function to add or remove sugars, add sulfate groups, and perform other modifications. Enzymes located within the cisterna modifies the vesicles carrying cargo proteins. New vesicles carrying the cargo proteins bud from the cisterna and travel to the next stable cisterna, where the next series of enzymes further processes the protein cargo.

D) Protein trafficking in Golgi of mammalian cells can be best explained by the cisternal maturation model.

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