Question

1. You are studying a protein, Y, that is predicted to be an integral membrane protein. Sequence analysis suggests the following: (18 points)

1. The protein has 7 transmembrane domains spaced evenly in the middle of the protein.
2. At the extreme N-terminus is a sensing domain that detects glucose levels.
3. At the extreme C-terminus is a protein domain that resembles a kinase domain.   This domain is incredibly likely to be intracellular. You have data to suggest that this domain interacts with cytosolic Protein Z in the way kinases typically do.
4. In between the last transmembrane domain and the C-terminal domain is a domain of unknown function. We’ll call it domain X. It is cytosolic.

a. Draw and label a picture of this protein, Y, in the membrane. Be sure to include all the relevant domains (6 points)

b. If you were to make a deletion construction of everything except for the extreme C-terminus, such that the kinase domain is the only thing expressed, where would it be expressed? How do you know? (4 points)

c. What two (opposite) outcomes might you expect if you were to express just this construct? (4 points)

Answer 1

1. Please find the protein image attached.

2. If only kinase domain, i. e extreme C terminal is expressed, it will be expressed in the cytosol. Since it does not have hydrophobic region, it will be functional in the cytosol.
3. If only this is expressed we can expect that the protein can no longer detect and bind to glucose.
Another possibility is that, the loss of region X of unknown function might cause constitutive autophoshorylation of kinase domain. if this is true, then the kinase domain might still be able to bind to protein Z and initiate down stream signalling.