You have engineered a fusion protein composed of a cis Golgi resident protein and the green fluorescent protein. Similarly, you have made a fusion protein composed of a trans Golgi protein and the red fluorescent protein. You express these proteins in cells and follow individual Golgi cisternae using fluorescence microscopy. You observe that each individual cisterna emits a green, faint yellow, or red fluorescent signal at different times: it initially shows green fluorescence, but the green fluorescent signal fades away with time, and instead red fluorescence appears in the same cisterna. Additionally, you do not observe any red fluorescent cisterna that becomes green over time. Do these observations agree better with the cisternal maturation model (C) or the vesicle transport model (V) for the organization of Golgi stacks? Write down C or V as your answer.

Question

Quizplus · Accepted Answer

The cisternal maturation model predicts that each cisterna matures over time, acquiring new components (as well as red fluorescence) as it matures, and recycling old components (green fluorescence) to the less mature cisternae by retrograde vesicle transport. The vesicle transport model predicts that each cisterna remains stationary and fluoresces either red (or yellow) or green during the entire period.

You Have Engineered a Fusion Protein Composed of a Cis