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Peripheral membrane proteins, or extrinsic membrane proteins, are membrane proteins that adhere only temporarily to the biological membrane with which they are associated. These proteins attach to integral membrane proteins, or penetrate the peripheral regions of the lipid bilayer. The regulatory protein subunits of many ion channels and transmembrane receptors, for example, may be defined as peripheral membrane proteins. In contrast to integral membrane proteins, peripheral membrane proteins tend to collect in the water-soluble component, or fraction, of all the proteins extracted during a protein purification procedure. Proteins with GPI anchors are an exception to this rule and can have purification properties similar to those of integral membrane proteins.
The plasma membranes of cells contain combinations of glycosphingolipids, cholesterol and protein receptors organised in glycolipoprotein lipid microdomains termed lipid rafts. Their existence in cellular membranes remains controversial. Indeed, Kervin and Overduin imply that lipid rafts are misconstrued protein islands, which they propose form through a proteolipid code. Nonetheless, it has been proposed that they are specialized membrane microdomains which compartmentalize cellular processes by serving as organising centers for the assembly of signaling molecules, allowing a closer interaction of protein receptors and their effectors to promote kinetically favorable interactions necessary for the signal transduction. Lipid rafts influence membrane fluidity and membrane protein trafficking, thereby regulating neurotransmission and receptor trafficking. Lipid rafts are more ordered and tightly packed than the surrounding bilayer, but float freely within the membrane bilayer. Although more common in the cell membrane, lipid rafts have also been reported in other parts of the cell, such as the Golgi apparatus and lysosomes.
Phosphatidylinositol or inositol phospholipid is a biomolecule. It was initially called "inosite" when it was discovered by Léon Maquenne and Johann Joseph von Scherer in the late 19th century. It was discovered in bacteria but later also found in eukaryotes, and was found to be a signaling molecule.
Phosphoinositide phospholipase C is a family of eukaryotic intracellular enzymes that play an important role in signal transduction processes. These enzymes belong to a larger superfamily of Phospholipase C. Other families of phospholipase C enzymes have been identified in bacteria and trypanosomes. Phospholipases C are phosphodiesterases.
Phosphatidylinositol 4,5-bisphosphate or PtdIns(4,5)P2, also known simply as PIP2 or PI(4,5)P2, is a minor phospholipid component of cell membranes. PtdIns(4,5)P2 is enriched at the plasma membrane where it is a substrate for a number of important signaling proteins. PIP2 also forms lipid clusters that sort proteins.
Pleckstrin homology domain or (PHIP) is a protein domain of approximately 120 amino acids that occurs in a wide range of proteins involved in intracellular signaling or as constituents of the cytoskeleton.
Phospholipase D (EC 3.1.4.4, lipophosphodiesterase II, lecithinase D, choline phosphatase, PLD; systematic name phosphatidylcholine phosphatidohydrolase) is an enzyme of the phospholipase superfamily that catalyses the following reaction
Surfactin is a cyclic lipopeptide, commonly used as an antibiotic for its capacity as a surfactant. It is an amphiphile capable of withstanding hydrophilic and hydrophobic environments. The Gram-positive bacterial species Bacillus subtilis produces surfactin for its antibiotic effects against competitors. Surfactin showcases antibacterial, antiviral, antifungal, and hemolytic effects.
David S. Cafiso is an American biochemist and a professor of chemistry at the University of Virginia. His research focuses on membrane proteins and cell signaling, and is primarily supported by grants from the National Institute of Health.
Pleckstrins are a family of proteins found in platelets and other cells. The name derives from platelet and leukocyteC kinase substrate and the KSTR string of amino acids. The prototype protein, now called pleckstrin-1, was first identified in 1979 as the major substrate of protein kinase C in platelets. The homolog pleckstrin-2 is more widely expressed in tissues.
Phospholipase D2 is an enzyme that in humans is encoded by the PLD2 gene.
α-Parinaric acid is a conjugated polyunsaturated fatty acid. Discovered by Tsujimoto and Koyanagi in 1933, it contains 18 carbon atoms and 4 conjugated double bonds. The repeating single bond-double bond structure of α-parinaric acid distinguishes it structurally and chemically from the usual "methylene-interrupted" arrangement of polyunsaturated fatty acids that have double-bonds and single bonds separated by a methylene unit (−CH2−). Because of the fluorescent properties conferred by the alternating double bonds, α-parinaric acid is commonly used as a molecular probe in the study of biomembranes.
Phospholipase C (PLC) is a class of membrane-associated enzymes that cleave phospholipids just before the phosphate group (see figure). It is most commonly taken to be synonymous with the human forms of this enzyme, which play an important role in eukaryotic cell physiology, in particular signal transduction pathways. Phospholipase C's role in signal transduction is its cleavage of phosphatidylinositol 4,5-bisphosphate (PIP2) into diacyl glycerol (DAG) and inositol 1,4,5-trisphosphate (IP3), which serve as second messengers. Activators of each PLC vary, but typically include heterotrimeric G protein subunits, protein tyrosine kinases, small G proteins, Ca2+, and phospholipids.
1-Phosphatidylinositol-4,5-bisphosphate phosphodiesterase beta-2 is an enzyme that in humans is encoded by the PLCB2 gene.
1-Phosphatidylinositol-4,5-bisphosphate phosphodiesterase delta-3 is an enzyme that in humans is encoded by the PLCD3 gene.
Membrane fusion is a key biophysical process that is essential for the functioning of life itself. It is defined as the event where two lipid bilayers approach each other and then merge to form a single continuous structure. In living beings, cells are made of an outer coat made of lipid bilayers; which then cause fusion to take place in events such as fertilization, embryogenesis and even infections by various types of bacteria and viruses. It is therefore an extremely important event to study. From an evolutionary angle, fusion is an extremely controlled phenomenon. Random fusion can result in severe problems to the normal functioning of the human body. Fusion of biological membranes is mediated by proteins. Regardless of the complexity of the system, fusion essentially occurs due to the interplay of various interfacial forces, namely hydration repulsion, hydrophobic attraction and van der Waals forces.
In membrane biology, fusion is the process by which two initially distinct lipid bilayers merge their hydrophobic cores, resulting in one interconnected structure. If this fusion proceeds completely through both leaflets of both bilayers, an aqueous bridge is formed and the internal contents of the two structures can mix. Alternatively, if only one leaflet from each bilayer is involved in the fusion process, the bilayers are said to be hemifused. In hemifusion, the lipid constituents of the outer leaflet of the two bilayers can mix, but the inner leaflets remain distinct. The aqueous contents enclosed by each bilayer also remain separated.
Sarah L. Keller is an American biophysicist, studying problems at the intersection between biology and chemistry. She investigates self-assembling soft matter systems. Her current main research focus is understanding how simple lipid mixtures within bilayer membranes give rise to membrane's complex phase behavior.
PIP2 domains are a type of cholesterol-independent lipid domain formed from phosphatidylinositol and positively charged proteins in the plasma membrane. They tend to inhibit GM1 lipid raft function.
Linda Columbus is an American chemist who is Professor of Chemistry and Molecular Physiology at the University of Virginia. Her research considers the structure-function properties of membrane proteins.
References
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- ↑ Rholam, Mohamed; Scarlata, Suzanne; Weber, Gregorio (1984-12-18). "Frictional resistance to the local rotations of fluorophores in proteins". Biochemistry. 23 (26): 6793–6796. doi:10.1021/bi00321a079. ISSN 0006-2960.
- ↑ Scarlata, Suzanne; Rholam, Mohamed; Weber, Gregorio (1984-12-18). "Frictional resistance to local rotations of aromatic fluorophores in some small peptides". Biochemistry. 23 (26): 6789–6792. doi:10.1021/bi00321a078. ISSN 0006-2960.
- ↑ Scarlata, Suzanne Frances; Ropp, Traci; Royer, Catherine A. (1989-08-08). "Histone subunit interactions as investigated by high pressure". Biochemistry. 28 (16): 6637–6641. doi:10.1021/bi00442a016. ISSN 0006-2960. PMID 2790018.
- ↑ Scarlata, S.F. (1991). "Compression of lipid membranes as observed at varying membrane positions". Biophysical Journal. 60 (2): 334–340. Bibcode:1991BpJ....60..334S. doi:10.1016/s0006-3495(91)82058-6. ISSN 0006-3495. PMC 1260069 . PMID 1912276.
- ↑ Runnels, Loren W.; Jenco, John; Morris, Andrew; Scarlata, Suzanne (1996-01-01). "Membrane Binding of Phospholipases C-β1 and C-β2 Is Independent of Phosphatidylinositol 4,5-Bisphosphate and the α and βγ Subunits of G Proteins". Biochemistry. 35 (51): 16824–16832. doi:10.1021/bi961606w. ISSN 0006-2960. PMID 8988021.
- ↑ Rosewitz, Jessica A.; Wang, Shuai; Scarlata, Suzanne F.; Rahbar, Nima (2021-06-01). "An enzymatic self-healing cementitious material". Applied Materials Today. 23: 101035. doi: 10.1016/j.apmt.2021.101035 . ISSN 2352-9407. S2CID 234837645.
- ↑ Guimapang, Katherine (June 21, 2021). "Researchers develop a feasible solution for self-healing concrete in the construction industry". Archinect. Retrieved 2022-01-07.
- ↑ "AAAS Announces Leading Scientists Elected as 2020 Fellows | American Association for the Advancement of Science". www.aaas.org. Retrieved 2022-01-07.
