An integral membrane protein (IMP) is a protein molecule (or assembly of proteins) that is permanently attached to the biological membrane. Proteins that cross the membrane are surrounded by "annular" lipids, which are defined as lipids that are in direct contact with a membrane protein. Such proteins can be separated from the biological membranes only using detergents, nonpolar solvents, or sometimes denaturing agents.
IMPs comprise a very significant fraction of the proteins encoded in an organism's genome.
All transmembrane proteins are IMPs, but not all IMPs are transmembrane proteins.
Read more about Integral Membrane Protein: Structure, Function, Examples
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