|
Major Intrinsic Proteins
Major intrinsic proteins comprise a large superfamily of transmembrane protein channels that are grouped together on the basis of homology. The MIP superfamily includes three subfamilies: aquaporins, aquaglyceroporins and S-aquaporins. # The aquaporins (AQPs) are water selective. # The aquaglyceroporins are permeable to water, but also to other small uncharged molecules such as glycerol. # The third subfamily, with little conserved amino acid sequences around the NPA boxes, include ' superaquaporins' (S-aquaporins). The phylogeny of insect MIP family channels has been published. Families There are two families that belong to thMIP Superfamily 1.A.8- The Major Intrinsic Protein (MIP) Family 1.A.16- The Formate-Nitrite Transporter (FNT) Family The Major Intrinsic Protein Family (TC# 1.A.8) The MIP family is large and diverse, possessing thousands of members that form transmembrane channels. These channel proteins function in transporting water, small carbohydrates (e.g., gly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aquaporin
Aquaporins, also called water channels, are channel proteins from a larger family of major intrinsic proteins that form pores in the membrane of biological cells, mainly facilitating transport of water between cells. The cell membranes of a variety of different bacteria, fungi, animal and plant cells contain aquaporins through which water can flow more rapidly into and out of the cell than by diffusing through the phospholipid bilayer. Aquaporins have six membrane-spanning alpha helical domains with both carboxylic and amino terminals on the cytoplasmic side. Two hydrophobic loops contain conserved asparagine- proline-alanine ("NPA motif") which form a barrel surrounding a central pore-like region that contains additional protein density. Because aquaporins are usually always open and are prevalent in just about every cell type, this leads to a misconception that water readily passes through the cell membrane down its concentration gradient. Water can pass through the cell mem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aquaporin 2
Aquaporin-2 (AQP-2) is found in the apical cell membranes of the kidney's collecting duct principal cells and in intracellular vesicles located throughout the cell. It is encoded by the gene. Regulation It is the only aquaporin regulated by vasopressin. The basic job of aquaporin 2 is to reabsorb water from the urine while its being removed from the blood by the kidney. Aquaporin 2 is in kidney epithelial cells and usually lies dormant in intracellular vesicle membranes. When it is needed, vasopressin binds to the cell surface vasopressin receptor thereby activating a signaling pathway that causes the aquaporin 2 containing vesicles to fuse with the plasma membrane, so the aquaporin 2 can be used by the cell. This aquaporin is regulated in two ways by the peptide hormone vasopressin: * short-term regulation (minutes) through trafficking of AQP2 vesicles to the apical region where they fuse with the apical plasma membrane * long-term regulation (days) through an increase in ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Family
A protein family is a group of evolutionarily related proteins. In many cases, a protein family has a corresponding gene family, in which each gene encodes a corresponding protein with a 1:1 relationship. The term "protein family" should not be confused with Family (biology), family as it is used in taxonomy. Proteins in a family descend from a common ancestor and typically have similar protein structure, three-dimensional structures, functions, and significant Sequence homology, sequence similarity. The most important of these is sequence similarity (usually amino-acid sequence), since it is the strictest indicator of homology and therefore the clearest indicator of common ancestry. A fairly well developed framework exists for evaluating the significance of similarity between a group of sequences using sequence alignment methods. Proteins that do not share a common ancestor are very unlikely to show statistically significant sequence similarity, making sequence alignment a powerf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Superfamily
A protein superfamily is the largest grouping (clade) of proteins for which common ancestry can be inferred (see homology (biology), homology). Usually this common ancestry is inferred from structural alignment and mechanistic similarity, even if no sequence similarity is evident. Sequence homology can then be deduced even if not apparent (due to low sequence similarity). Superfamilies typically contain several protein families which show sequence similarity within each family. The term ''protein clan'' is commonly used for protease and glycosyl hydrolases superfamilies based on the MEROPS and CAZy classification systems. Identification Superfamilies of proteins are identified using a number of methods. Closely related members can be identified by different methods to those needed to group the most evolutionarily divergent members. Sequence similarity Historically, the similarity of different amino acid sequences has been the most common method of inferring Sequence homology, h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Integral Membrane Protein
An integral, or intrinsic, membrane protein (IMP) is a type of membrane protein that is permanently attached to the biological membrane. All ''transmembrane proteins'' are IMPs, but not all IMPs are transmembrane proteins. IMPs comprise a significant fraction of the proteins encoded in an organism's genome. 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 only be separated from the membranes by using detergents, nonpolar solvents, or sometimes denaturing agents. Structure Three-dimensional structures of ~160 different integral membrane proteins have been determined at atomic resolution by X-ray crystallography or nuclear magnetic resonance spectroscopy. They are challenging subjects for study owing to the difficulties associated with extraction and crystallization. In addition, structures of many water-soluble protein domains of IMPs are available in the Prote ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aquaporin
Aquaporins, also called water channels, are channel proteins from a larger family of major intrinsic proteins that form pores in the membrane of biological cells, mainly facilitating transport of water between cells. The cell membranes of a variety of different bacteria, fungi, animal and plant cells contain aquaporins through which water can flow more rapidly into and out of the cell than by diffusing through the phospholipid bilayer. Aquaporins have six membrane-spanning alpha helical domains with both carboxylic and amino terminals on the cytoplasmic side. Two hydrophobic loops contain conserved asparagine- proline-alanine ("NPA motif") which form a barrel surrounding a central pore-like region that contains additional protein density. Because aquaporins are usually always open and are prevalent in just about every cell type, this leads to a misconception that water readily passes through the cell membrane down its concentration gradient. Water can pass through the cell mem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MIPModDB
MIPModDB is a database of comparative protein structure models of MIP (Major intrinsic proteins) family of proteins. See also * Major intrinsic proteins Major intrinsic proteins comprise a large superfamily of transmembrane protein channels that are grouped together on the basis of homology. The MIP superfamily includes three subfamilies: aquaporins, aquaglyceroporins and S-aquaporins. # The aqua ... References External links * http://bioinfo.iitk.ac.in/MIPModDB. Biological databases Protein domains Protein families Transmembrane proteins {{Biodatabase-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MIP (gene)
Lens fiber major intrinsic protein also known as aquaporin-0 is a protein that in humans is encoded by the ''MIP'' gene. Function Major intrinsic protein is a member of the water-transporting aquaporins as well as the original member of the MIP family of channel proteins. The function of the fiber cell membrane protein encoded by this gene is undetermined, yet this protein is speculated to play a role in intracellular communication. The MIP protein is expressed in the ocular lens and is required for correct lens function. This gene has been mapped among aquaporins AQP2 Aquaporin-2 (AQP-2) is found in the apical cell membranes of the kidney's collecting duct principal cells and in intracellular vesicles located throughout the cell. It is encoded by the gene. Regulation It is the only aquaporin regulated by ..., AQP5, and AQP6, in a potential gene cluster at 12q13. References Further reading * * * * * * * * * * * * * * * * * {{gene-12-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AQP9
Aquaporin-9 (AQP-9) is a protein that in humans is encoded by the ''AQP9'' gene. The aquaporin Aquaporins, also called water channels, are channel proteins from a larger family of major intrinsic proteins that form pores in the membrane of biological cells, mainly facilitating transport of water between cells. The cell membranes of a v ...s/ major intrinsic protein are a family of water-selective membrane channels. Aquaporin-9 has greater sequence similarity with AQP3 and AQP7 and they may be a subfamily. Aquaporin-9 allows passage of a wide variety of noncharged solutes. AQP-9 stimulates urea transport and osmotic water permeability; there are contradicting reports about its role in providing glycerol permeability. Aquaporin-9 may also have some role in specialized leukocyte functions such as immunological response and bactericidal activity. References Further reading * * * * * * * * * * * * * * External links * * {{Ion channels, g4 [Baidu] |
AQP8
Aquaporin-8 is a protein that in humans is encoded by the ''AQP8'' gene. Aquaporin-8 (AQP-8) is a water channel protein. Aquaporin Aquaporins, also called water channels, are channel proteins from a larger family of major intrinsic proteins that form pores in the membrane of biological cells, mainly facilitating transport of water between cells. The cell membranes of a ...s are a family of small integral membrane proteins related to the major intrinsic protein (MIP or AQP0). Aquaporin-8 mRNA is found in pancreas and colon but not other tissues. References Further reading * * * * * * * * * * External links * * {{Ion channels, g4 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AQP7
Aquaporin-7 (AQP-7) is a protein that in humans is encoded by the ''AQP7'' gene. Aquaporins/major intrinsic proteins Major intrinsic proteins comprise a large superfamily of transmembrane protein channels that are grouped together on the basis of homology. The MIP superfamily includes three subfamilies: aquaporins, aquaglyceroporins and S-aquaporins. # The aqua ... (MIP) are a family of water-selective membrane channels. Aquaporin-7 has greater sequence similarity with AQP3 and AQP9 and they may be a subfamily. Aquaporin-7 and AQP3 are at the same chromosomal location suggesting that 9p13 may be a site of an aquaporin cluster. Aquaporin-7 facilitates water, glycerol and urea transport. It may play an important role in thermoregulation in the form of perspiration, and sperm function. References Further reading * * * * * * * * * * * * External links * * * {{Ion channels, g4 [Baidu] |
