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An Integral Membrane Protein (IMP) is a protein molecule (or assembly of proteins) that is permanently attached to the biological membrane. Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by MembraneA biological membrane or biomembrane is an enclosing or separating Amphipathic layer that acts as a barrier within or around a cell. Such proteins can be separated from the biological membranes only using detergents, nonpolar solvents, or sometimes denaturing agents. A detergent (as a noun is a material intended to assist Cleaning. A solvent is a liquid or gas that dissolves a solid liquid or gaseous Solute, resulting in a Solution. Denaturation is a process in which Proteins or Nucleic acids lose their structure (tertiary structure by application of some external stress or compound for

IMPs comprise a very significant fraction of the proteins encoded in the genome. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby

Contents

Structure

Three-dimensional structures of only ~160 different integral membrane proteins are currently determined at atomic resolution by X-ray crystallography or Nuclear magnetic resonance spectroscopy due to the difficulties with extraction and crystallization. X-ray crystallography is a method of determining the arrangement of Atoms within a Crystal, in which a beam of X-rays strikes a crystal and scatters Spectroscopy was originally the study of the interaction between Radiation and Matter as a function of Wavelength (λ In addition, structures of many water-soluble domains of IMPs are available in the Protein Data Bank. The Protein Data Bank ( PDB) is a repository for 3-D structural data of Proteins and Nucleic acids These data typically obtained by X-ray crystallography Their membrane-anchoring α-helices have been removed to facilitate the extraction and crystallization.

IMPs can be divided into two groups:

  1. Transmembrane proteins
  2. Integral monotopic proteins

Integral transmembrane protein

Main article: Transmembrane proteins

The most common type of IMP is the transmembrane protein (TM), which spans the entire biological membrane. A transmembrane protein is a Protein that spans the entire Biological membrane. Peripheral membrane proteins are Proteins that adhere only temporarily to the Biological membrane with which they are associated A transmembrane protein is a Protein that spans the entire Biological membrane. A transmembrane protein is a Protein that spans the entire Biological membrane. MembraneA biological membrane or biomembrane is an enclosing or separating Amphipathic layer that acts as a barrier within or around a cell. Such a protein may cross the membrane only once or it may weave in and out, crossing several times. TM proteins can be categorized as Type I, which are positioned such that their amino-terminus is outside of the membrane, or Type II, which have their carboxy-terminus outside of the membrane.

Integral monotopic proteins

Integral monotopic proteins are permanently attached to the membrane from one side.

Main article: Peripheral membrane protein

Three-dimensional structures of the following integral monotopic proteins have been determined:

There are also structures of integral monotopic domains of transmembrane proteins:

Such domains require detergents for extraction or crystallization, even after removal of their transmembrane helices. Therefore, they are often classified as integral monotopic proteins [9]

Function

IMPs include transporters, channels, receptors, enzymes, structural membrane-anchoring domains, proteins involved in accumulation and transduction of energy, and proteins responsible for cell adhesion. Ion channels are pore-forming Proteins that help establish and control the small Voltage Gradient across the Plasma membrane of all living In Biochemistry, a receptor is a Protein molecule embedded in either the Plasma membrane or Cytoplasm of a cell to which a mobile signaling Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins In Biophysics, transduction is the conveyance of energy from one Electron (a donor to another (a receptor at the same time that the class of energy changes Cellular adhesion is the binding of a cell to another cell or to a Surface or matrix. Classification of transporters can be found in TCDB database.

References

See also

Examples

Examples of integral membrane proteins:

External links

Also see Transmembrane protein. A membrane protein is a Protein molecule that is attached to or associated with the membrane A transmembrane protein is a Protein that spans the entire Biological membrane. Peripheral membrane proteins are Proteins that adhere only temporarily to the Biological membrane with which they are associated Integrins are Cell surface receptors that interact with the Extracellular matrix (ECM and mediate various intracellular signals. Cadherins are a class of type-1 Transmembrane proteins They play important roles in Cell adhesion, ensuring that cells within tissues are bound together In Molecular biology, the insulin receptor is a transmembrane receptor that is activated by Insulin. Neural Cell Adhesion Molecule (NCAM also the Cluster of differentiation CD56) is a homophilic binding glycoprotein expressed on the surface of Neurons, Selectins are a family of cell adhesion Molecules (or CAMs. All selectins are single-chain transmembrane Glycoproteins that share similar properties Cellular adhesion is the binding of a cell to another cell or to a Surface or matrix. Transmembrane receptors are Integral membrane proteins which reside and operate typically within a cell's Plasma membrane, but also in the membranes of A Glycophorin is a Sialoglycoprotein of the Membrane of a Red blood cell. Rhodopsin, also known as visual purple, is a Pigment of the Retina that is responsible for both the formation of the Photoreceptor cells and the Anion Exchanger 1 ( AE1) or Band 3 is a Phylogenetically preserved Transport protein responsible for mediating the electroneutral exchange of CD36 ( C luster of D ifferentiation 36 is an Integral membrane protein found on the surface of many cell types in vertebrate animals and is also known as
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