Question

3. You are characterizing an isolated membrane protein. The protein is exposed on both sides of the membrane. Over much of the central part of its surface, there are hydrophobic amino acids, while the ends are hydrophilic. It crosses the membrane a number of times. There is an opening in the center of this protein lined by hydrophilic amino acids. What kind of protein is this and what is its probable function?

Answer 1

It is a transmembrane protein. We know that the cell membrane is made up of lipid bilayer. So the interior portion is highly hydrophobic in nature. Here it is said that the central part of the part is made up of hydrophobic amino acids. So this region must be present inside the membrane and the hydrophilic part must towards both sides. Here it is also said that there is an opening in the center of the protein and this opening is lined by hydrophilic amino acids. So our protein of interest must be a Transport Protein that allows the passage of hydrophilic particles across the membrane. We already know that hydrophilic particles cannot pass their own across the membrane. So they require these kinds of transport proteins.

Transport proteins are of different types:

• Channel proteins
• Carrier proteins
• Gate proteins