Question

Proteins $P,Q$, and $R$ are associated with intact organellar membrane in a cell. If the intact organelle is treated with a high ionic strength buffer, only protein $R$ remained associated with the membrane fraction. Based on this, one could conclude that

• A. $P$ and $Q$ are peripheral membrane proteins.
• B. $R$ is a peripheral membrane protein.
• C. $P$ and $Q$ are integral membrane bound proteins.
• D. $P$ is peripheral and $Q$ is integral membrane protein.

Answer 1

Answer: (A)

$P$ and $Q$ are peripheral membrane proteins.

Peripheral membrane proteins are membrane proteins that adhere only temporarily to the biological membrane. They are attached to surface of membrane by electrostatic, hydrogen‐bonding or hydrophobic interactions. High ionic strength buffer like 0.4 M NaCl can be used to disintegrate the peripheral membrane proteins. peripheral membrane proteins can also be released from the cell by using extreme pH or chaotropic agents. However, integral membrane proteins are not easily disintegrated by such agents. They remain associated wit the membrane fraction.

Thus, the correct answer is option A.