Membrane protein
Membrane proteins are common proteins that are part of, or interact with, biological membranes. Membrane proteins fall into several broad categories depending on their location. Integral membrane proteins are a permanent part of a cell membrane and can either penetrate the membrane (transmembrane) or associate with one or the other side of a membrane (integral monotopic). Peripheral membrane proteins are transiently associated with the cell membrane.
Membrane proteins are common, and medically important—about a third of all human proteins are membrane proteins, and these are targets for more than half of all drugs.[1] Nonetheless, compared to other classes of proteins, determining membrane protein structures remains a challenge in large part due to the difficulty in establishing experimental conditions that can preserve the correct conformation of the protein in isolation from its native environment.
Function
Membrane proteins perform a variety of functions vital to the survival of organisms:[2]
- environments.
- Transporter Classification database.
- Membrane
- Cell adhesion molecules allow cells to identify each other and interact. For example, proteins involved in immune response
The localization of proteins in membranes can be predicted reliably using
Integral membrane proteins
- These proteins have one of two structural architectures:
- biological membranes;
- chloroplasts.[6]
- Bitopic proteins are transmembrane proteins that span across the membrane only once. Transmembrane helices from these proteins have significantly different amino acid distributions to transmembrane helices from polytopic proteins.[7]
- Integral monotopic proteins are integral membrane proteins that are attached to only one side of the membrane and do not span the whole way across.
Peripheral membrane proteins
Integral and peripheral proteins may be post-translationally modified, with added
Polypeptide toxins
In genomes
Membrane proteins, like soluble
In disease
Membrane proteins are the
Purification of membrane proteins
Although membrane proteins play an important role in all organisms, their purification has historically, and continues to be, a huge challenge for protein scientists. In 2008, 150 unique structures of membrane proteins were available,
See also
- Annular lipid shell
- Carrier protein
- Inner nuclear membrane proteins
- Ion channel
- Ion pump (biology)
- List of MeSH codes (D12.776)
- Receptor (biochemistry)
- TMPad (TransMembrane Protein Helix-Packing Database)
- Transmembrane proteins
References
Further reading
- Johnson JE, Cornell RB (1999). "Amphitropic proteins: regulation by reversible membrane interactions (review)". PMID 10503244.
- Alenghat FJ, Golan DE (2013). "Membrane protein dynamics and functional implications in mammalian cells". Current Topics in Membranes. 72: 89–120. PMID 24210428.
External links
Organizations
- Membrane Protein Structural Dynamics Consortium
- Experts for Membrane Protein Research and Purification
Membrane protein databases
- TCDB - Transporter Classification database, a comprehensive classification of transmembrane transporter proteins
- Orientations of Proteins in Membranes (OPM) database - 3D structures of integral and peripheral membrane proteins arranged in the lipid bilayer
- Protein Data Bank of Transmembrane Proteins - 3D models of transmembrane proteins approximately arranged in the lipid bilayer.
- TransportDB - Genomics-oriented database of transporters from TIGR
- Membrane PDB Archived 2020-08-03 at the Wayback Machine - Database of 3D structures of integral membrane proteins and hydrophobic peptides with an emphasis on crystallization conditions
- Mpstruc database Archived 2013-12-25 at the Wayback Machine - A curated list of selected transmembrane proteins from the Protein Data Bank
- MemProtMD - a database of membrane protein structures simulated by coarse-grained molecular dynamics
- bitopic proteinsfrom several model organisms