Integral membrane proteins (IMPs) span the entire cell membrane and are permanently attached. They are classified into two groups: transmembrane and monotopic. Transmembrane IMPs are the most common and include receptors, transporters, and transmitters. Monotopic IMPs are attached to the membrane on one side and include enzymes. IMPs can only be removed with specific chemical treatments.
An integral membrane protein, also known as an IMP, is one that spans the entire biological membrane of a cell. These proteins are permanently attached to the cell membrane and their function typically relies on being present in the membrane. Both structurally and functionally, they are integral parts of cell membranes.
Each integral membrane protein molecule has an intricate relationship with the membrane within which it is found. Structurally, the IMP is usually positioned such that protein strands are intertwined throughout the cell membrane structure. Sections of proteins protrude through the cell wall into or out of the cell, or in both directions. The protein molecule cannot function if it is not incorporated into the membrane.
Another feature of the protein is that these proteins can only be removed from the membrane with a very specific chemical treatment. This is because the hydrophobic regions of the protein are protected within the phospholipid bilayer of the cell membrane. For this reason, detergents, denaturing solvents, and non-polar solvents must be used to disrupt the phospholipid bilayer and extract the integral membrane protein.
Within the class of integral membrane proteins are several categories of proteins, many of which are receptors and other types of cell signaling molecules. They are classified into two groups, based on their structure. These are transmembrane integral proteins and monotopic integral proteins.
Integral transmembrane proteins are those that span the entire cell membrane. These proteins can cross the membrane once, or they can cross it multiple times, intertwining through the phospholipid bilayer such that there are different pieces of the protein sticking out through the cell wall. Overall this is the most common type of IMP.
Examples of integral transmembrane proteins include voltage-gated ion channels such as those that transport potassium ions in and out of cells. Certain types of T cell receptors, the insulin receptor and many other receptors and neurotransmitters are all integral transmembrane proteins. In general, receptors, transmitters, and transporters tend to belong to this class of IMPs because proteins that span the entire membrane are typically capable of sensing conditions both inside and outside the cell simultaneously.
Integral monotopic proteins do not cover the entire biological membrane. Instead they are attached to the membrane on only one side, with one end of the protein protruding into or out of the cell. This class of proteins includes enzymes such as monoamine oxidase and fatty acid amide hydrolase. Monotopic integral proteins are unable to sense conditions both inside and outside the cell and are less likely to be involved in intercellular signaling.
Protect your devices with Threat Protection by NordVPN
