In molecular biology, molecular chaperones are proteins that assist the conformational folding or unfolding of large proteins or macromolecular protein complexes. There are a number of classes of molecular chaperones, all of which function to assist large proteins in proper protein folding during or after synthesis, and after partial denaturation. Chaperones are also involved in the translocation of proteins for proteolysis.
Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classical mechanism of cell secretion is via secretory portals at the plasma membrane called porosomes. Porosomes are permanent cup-shaped lipoprotein structures embedded in the cell membrane, where secretory vesicles transiently dock and fuse to release intra-vesicular contents from the cell.
Autophagy is the natural, conserved degradation of the cell that removes unnecessary or dysfunctional components through a lysosome-dependent regulated mechanism. It allows the orderly degradation and recycling of cellular components. Although initially characterized as a primordial degradation pathway induced to protect against starvation, it has become increasingly clear that autophagy also plays a major role in the homeostasis of non-starved cells. Defects in autophagy have been linked to various human diseases, including neurodegeneration and cancer, and interest in modulating autophagy as a potential treatment for these diseases has grown rapidly.
A structural gene is a gene that codes for any RNA or protein product other than a regulatory factor. A term derived from the lac operon, structural genes are typically viewed as those containing sequences of DNA corresponding to the amino acids of a protein that will be produced, as long as said protein does not function to regulate gene expression. Structural gene products include enzymes and structural proteins. Also encoded by structural genes are non-coding RNAs, such as rRNAs and tRNAs.
Diphtheria toxin is an exotoxin secreted mainly by Corynebacterium diphtheriae but also by Corynebacterium ulcerans and Corynebacterium pseudotuberculosis, the pathogenic bacterium that causes diphtheria. The toxin gene is encoded by a prophage called corynephage β. The toxin causes the disease in humans by gaining entry into the cell cytoplasm and inhibiting protein synthesis.
The Von Hippel–Lindau tumor suppressor also known as pVHL is a protein that, in humans, is encoded by the VHL gene. Mutations of the VHL gene are associated with Von Hippel–Lindau disease, which is characterized by hemangioblastomas of the brain, spinal cord and retina. It is also associated with kidney and pancreatic lesions.
Bacteria are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria play a vital role in many stages of the nutrient cycle by recycling nutrients and the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of dead bodies; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Bacteria also live in mutualistic, commensal and parasitic relationships with plants and animals. Most bacteria have not been characterised and there are many species that cannot be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.
The type III secretion system is one of the bacterial secretion systems used by bacteria to secrete their effector proteins into the host's cells to promote virulence and colonisation. While the type III secretion system has been widely regarded as equivalent to the injectisome, many argue that the injectisome is only part of the type III secretion system, which also include structures like the flagellar export apparatus. The T3SS is a needle-like protein complex found in several species of pathogenic gram-negative bacteria.
Treponema denticola is a Gram-negative, obligate anaerobic, motile and highly proteolytic spirochete bacterium. It is one of four species of oral spirochetes to be reliably cultured, the others being Treponema pectinovorum, Treponema socranskii and Treponema vincentii. T. denticola dwells in a complex and diverse microbial community within the oral cavity and is highly specialized to survive in this environment. T. denticola is associated with the incidence and severity of human periodontal disease. Treponema denticola is one of three bacteria that form the Red Complex, the other two being Porphyromonas gingivalis and Tannerella forsythia. Together they form the major virulent pathogens that cause chronic periodontitis. Having elevated T. denticola levels in the mouth is considered one of the main etiological agents of periodontitis. T. denticola is related to the syphilis-causing obligate human pathogen, Treponema pallidum subsp. pallidum. It has also been isolated from women with bacterial vaginosis.
Heat shock protein HSP 90-beta also called HSP90beta is a protein that in humans is encoded by the HSP90AB1 gene.
Elongin C is a protein that in humans is encoded by the ELOC gene.
Elongin B is a protein that in humans is encoded by the ELOB gene.
Cullin-2 is a protein that in humans is encoded by the CUL2 gene.
Fanconi anemia group J protein is a protein that in humans is encoded by the BRCA1-interacting protein 1 (BRIP1) gene.
Gabriel Waksman FMedSci, FRS, is Courtauld professor of biochemistry and molecular biology at University College London (UCL), and professor of structural and molecular biology at Birkbeck College, University of London. He is the director of the Institute of Structural and Molecular Biology (ISMB) at UCL and Birkbeck, head of the Department of Structural and Molecular Biology at UCL, and head of the Department of Biological Sciences at Birkbeck.
The type VI secretion system (T6SS) is molecular machine used by a wide range of Gram-negative bacterial species to transport effectors from the interior of a bacterial cell across the cellular envelope into an adjacent target cell. While often reported that the T6SS was discovered in 2006 by researchers studying the causative agent of cholera, Vibrio cholerae, the first study demonstrating that T6SS genes encode a protein export apparatus was actually published in 2004, in a study of protein secretion by the fish pathogen Edwardsiella tarda.
Daniel A. Portnoy is a microbiologist, the Edward E. Penhoet Distinguished Chair in Global Public Health and Infectious Diseases, and a Professor of Biochemistry, Biophysics and Structural Biology in the Department of Molecular and Cell Biology and in the Division of Microbiology in the Department of Plant and Microbial Biology at the University of California, Berkeley. He is one of the world's foremost experts on Listeria monocytogenes, the bacterium that causes the severe foodborne illness Listeriosis. He has made seminal contributions to multiple aspects of bacterial pathogenesis, cell biology, innate immunity, and cell mediated immunity using L. monocytogenes as a model system and has helped to push forward the use of attenuated L. monocytogenes as an immunotherapeutic tool in the treatment of cancer.
Bacterial secretion systems are protein complexes present on the cell membranes of bacteria for secretion of substances. Specifically, they are the cellular devices used by pathogenic bacteria to secrete their virulence factors to invade the host cells. They can be classified into different types based on their specific structure, composition and activity. Generally, proteins can be secreted through two different processes. One process is a one-step mechanism in which proteins from the cytoplasm of bacteria are transported and delivered directly through the cell membrane into the host cell. Another involves a two-step activity in which the proteins are first transported out of the inner cell membrane, then deposited in the periplasm, and finally through the outer cell membrane into the host cell.
Colin Hughes PhD ScD FLSW is a British microbiologist who has worked in the areas of bacterial virulence, motility and antibiotic resistance. He is Emeritus Professor of Microbiology at the University of Cambridge, Fellow of Trinity College Cambridge, and Fellow of the Learned Society of Wales.
Type VII secretion systems are bacterial secretion systems first observed in the phyla Actinomycetota and Bacillota. Bacteria use such systems to transport, or secrete, proteins into the environment. The bacterial genus Mycobacterium uses type VII secretion systems (T7SS) to secrete proteins across their cell envelope. The first T7SS system discovered was the ESX-1 System.
