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[[File:transmembrane_receptor.svg|left|transmembrane receptor|thumb]] [[File:Group_1_and_2_transmembrane_protein.png|left|Group 1 and 2 transmembrane protein|thumb|left]] '''Integral membrane proteins''' are [[proteins]] that are permanently attached to the [[membrane]] of [[cells]] or the membranes within [[cell]]s, such as the [[mitochondria]], [[endoplasmic reticulum]], and [[nucleus]]. These proteins play critical roles in various biological processes, including [[cell signaling]], [[transport]] of molecules across membranes, and [[cell adhesion]]. Integral membrane proteins can be classified based on their relationship with the membrane into [[transmembrane proteins]], which span the entire membrane, and monotopic proteins, which are attached to only one side of the membrane.

==Structure==
Integral membrane proteins have unique structural features that allow them to interact with the hydrophobic core of the [[lipid bilayer]]. The most common structure seen in these proteins is the [[alpha-helix]], but [[beta-barrels]] are also found, especially in [[bacterial outer membrane proteins]]. The hydrophobic amino acids of these proteins interact with the lipid tails within the membrane, while hydrophilic regions are exposed to the aqueous environment on either side of the membrane.

==Function==
The functions of integral membrane proteins are diverse and vital for the survival of the cell. They include:

* '''[[Transport proteins]]''': These proteins facilitate the movement of ions, small molecules, or macromolecules across membranes. Examples include [[ion channels]], [[carrier proteins]], and [[pumps]].
* '''[[Receptor proteins]]''': Integral membrane proteins can act as receptors that bind to [[ligands]] (such as hormones or neurotransmitters) and initiate cellular responses.
* '''[[Enzymes]]''': Some integral membrane proteins have enzymatic functions, catalyzing reactions that take place at the membrane interface.
* '''[[Structural proteins]]''': These proteins contribute to the shape and stability of the cell membrane.

==Classification==
Integral membrane proteins can be classified into two main types:

* '''[[Transmembrane proteins]]''': These proteins span the entire lipid bilayer. They can have one or more [[transmembrane domains]], which are typically alpha-helical but can also form beta-barrels.
* '''Monotopic proteins''': These are permanently attached to the membrane from only one side and do not span the entire membrane.

==Methods of Study==
Studying integral membrane proteins is challenging due to their hydrophobic nature and the difficulty in extracting them from membranes without disrupting their structure. Techniques used in their study include [[X-ray crystallography]], [[cryo-electron microscopy]], and [[nuclear magnetic resonance spectroscopy]]. These methods have contributed significantly to understanding the structure and function of integral membrane proteins.

==Biological Significance==
Integral membrane proteins are essential for the life of the cell. They are involved in processes such as [[cell communication]], [[immune response]], and [[metabolism]]. Disruptions in the function of these proteins can lead to diseases, including [[cystic fibrosis]], which is caused by a defect in the CFTR chloride channel, and various forms of [[cancer]].

[[Category:Proteins]]
[[Category:Membrane biology]]

{{biochemistry-stub}}

Integral membrane protein - Revision history

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