The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O group of the amino acid located four residues earlier along the protein sequence.
A transmembrane protein (TP) is a type of integral membrane protein that spans the entirety of the cell membrane. Many transmembrane proteins function as gateways to permit the transport of specific substances across the membrane. They frequently undergo significant conformational changes to move a substance through the membrane. They are usually highly hydrophobic and aggregate and precipitate in water. They require detergents or nonpolar solvents for extraction, although some of them (beta-barrels) can be also extracted using denaturing agents.
Beta-peptides (β-peptides) are peptides derived from β-amino acids. The parent β-amino acid is β-alanine (H2NCH2CH2CO2H), a common naturally occurring β amino acid, but most examples feature substituents in place of one or more C-H bonds. β-peptides usually do not occur in nature. β-peptide-based antibiotics are being explored as ways of evading antibiotic resistance. Early studies in this field were published in 1996 by the group of Dieter Seebach and that of Samuel Gellman.
Defensins are small cysteine-rich cationic proteins across cellular life, including vertebrate and invertebrate animals, plants, and fungi. They are host defense peptides, with members displaying either direct antimicrobial activity, immune signalling activities, or both. They are variously active against bacteria, fungi and many enveloped and nonenveloped viruses. They are typically 18-45 amino acids in length, with three or four highly conserved disulphide bonds.
Antimicrobial peptides (AMPs), also called host defence peptides (HDPs) are part of the innate immune response found among all classes of life. Fundamental differences exist between prokaryotic and eukaryotic cells that may represent targets for antimicrobial peptides. These peptides are potent, broad spectrum antibiotics which demonstrate potential as novel therapeutic agents. Antimicrobial peptides have been demonstrated to kill Gram negative and Gram positive bacteria, enveloped viruses, fungi and even transformed or cancerous cells. Unlike the majority of conventional antibiotics it appears that antimicrobial peptides frequently destabilize biological membranes, can form transmembrane channels, and may also have the ability to enhance immunity by functioning as immunomodulators.
In chemistry, a foldamer is a discrete chain molecule or oligomer that folds into a conformationally ordered state in solution. They are artificial molecules that mimic the ability of proteins, nucleic acids, and polysaccharides to fold into well-defined conformations, such as helices and β-sheets. The structure of a foldamer is stabilized by noncovalent interactions between nonadjacent monomers. Foldamers are studied with the main goal of designing large molecules with predictable structures. The study of foldamers is related to the themes of molecular self-assembly, molecular recognition, and host–guest chemistry.
Jules A. Hoffmann is a Luxembourg-born French biologist. During his youth, growing up in Luxembourg, he developed a strong interest in insects under the influence of his father, Jos Hoffmann. This eventually resulted in the younger Hoffmann's dedication to the field of biology using insects as model organisms. He currently holds a faculty position at the University of Strasbourg. He is a research director and member of the board of administrators of the National Center of Scientific Research (CNRS) in Strasbourg, France. He was elected to the positions of Vice-President (2005-2006) and President (2007-2008) of the French Academy of Sciences. Hoffmann and Bruce Beutler were jointly awarded a half share of the 2011 Nobel Prize in Physiology or Medicine for "their discoveries concerning the activation of innate immunity,". [More specifically, the work showing increased Drosomycin expression following activation of Toll pathway in microbial infection.]
Beta defensins are a family of vertebrate defensins. The beta defensins are antimicrobial peptides implicated in the resistance of epithelial surfaces to microbial colonization.
Plant defensins are a family of small, cysteine-rich defensins found in plants that serve to defend them against pathogens and parasites.
Arthropod defensins are a family defensin proteins found in mollusks, insects, and arachnids. These cysteine-rich antibacterial peptides are primarily active against Gram-positive bacteria and fungi in vitro. However Drosophila fruit flies mutant for the fly defensin were more susceptible to infection by the Gram-negative bacteria Providencia burhodogranariea, and resisted infection against Gram-positive bacteria like wild-type flies. It remains to be seen how in vitro activity relates to in vivo function. Mutants for the defensin-like antimicrobial peptide Drosomycin were more susceptible to fungi, validating a role for defensin-like peptides in anti-fungal defence.
Pseudin is a peptide derived from Pseudis paradoxa. Pseudins have some antimicrobial function.
Cecropins are antimicrobial peptides. They were first isolated from the hemolymph of Hyalophora cecropia, whence the term cecropin was derived. Cecropins lyse bacterial cell membranes; they also inhibit proline uptake and cause leaky membranes.
Latarcins are short antimicrobial peptides from the venom of the spider Lachesana tarabaevi. Latarcins adopt an amphipathic alpha-helical structure in the plasma membrane. Possible pharmacological applications for latarcins include antimicrobial and anticancer treatments.
Clavanin B is an alpha-helical antimicrobial peptide isolated from Styela clava.
Oxyopinins are a group of peptide toxins present in the venom of lynx spiders belonging to the genus Oxyopes, from which they derive their name.
Attacin is a glycine-rich protein of about 20 kDa belonging to the group of antimicrobial peptides (AMP). It is active against Gram-negative bacteria.
Drosomycin is an antifungal peptide from Drosophila melanogaster and was the first antifungal peptide isolated from insects. Drosomycin is induced by infection by the Toll signalling pathway, while expression in surface epithelia like the respiratory tract is instead controlled by the immune deficiency pathway (Imd). This means that drosomycin, alongside other antimicrobial peptides (AMPs) such as cecropins, diptericin, drosocin, metchnikowin and attacin, serves as a first line defence upon septic injury. However drosomycin is also expressed constitutively to a lesser extent in different tissues and throughout development.
Esculentin-2CHa is an antimicrobial peptide located outside the epithelial cell's membrane of the skin of many species of amphibians, such as Rana chiricahuensis. This peptide has recently become more important due to its defense response function and its possible application in the treatment of various human pathologies, that range from type 2 diabetes to bacterial and fungi infections. Esculentin-2CHa is a peptide that belongs to the Esculentin-2 family, which is known for its broad-spectrum of antimicrobial activity and its low cytotoxicity to human erythrocytes. However, not much is known about its structures and their relation to the functions these peptides carry out.
Fat body is a highly dynamic insect tissue composed primarily of storage cells. It is distributed throughout the insect's internal body cavity; the haemocoel, in close proximity to the epidermis, digestive organs and ovaries. Its main functions are nutrient storage and metabolism, for which it is commonly compared to a combination of adipose tissue and liver in mammals. However, it may also serve a variety of other roles, such as: endocrine regulation, systemic immunity, vitellogenesis, and main site of production of antimicrobial molecules called antimicrobial peptides.
Diptericin is a 9 kDa antimicrobial peptide (AMP) of flies first isolated from the blowfly Phormia terranova. It is primarily active against Gram-negative bacteria, disrupting bacterial membrane integrity. The structure of this protein includes a proline-rich domain with similarities to the AMPs drosocin, pyrrhocoricin, and abaecin, and a glycine-rich domain with similarity to attacin. Diptericin is an iconic readout of immune system activity in flies, used ubiquitously in studies of Drosophila immunity. Diptericin is named after the insect order Diptera.
