Question: What is the setting of Death's Domain?
Context: The HAMP domain (present in Histidine kinases, Adenylate cyclases, Methyl accepting proteins and Phosphatases) is an approximately 50-amino acid alpha-helical region that forms a dimeric, four-helical coiled coil.  It is found in bacterial sensor and chemotaxis proteins and in eukaryotic histidine kinases.  The bacterial proteins are usually integral membrane proteins and part of a two-component signal transduction pathway.  One or several copies of the HAMP domain can be found in association with other domains, such as the histidine kinase domain, the bacterial chemotaxis sensory transducer domain, the PAS repeat, the EAL domain, the GGDEF domain, the protein phosphatase 2C-like domain, the guanylate cyclase domain, or the response regulatory domain.  In its most common setting, the HAMP domain transmits conformational changes in periplasmic ligand-binding domains to cytoplasmic signalling kinase and methyl-acceptor domains and thus regulates the phosphorylation or methylation activity of homodimeric receptors. The death domain (DD) is a protein interaction module composed of a bundle of six alpha-helices.  DD is a subclass of protein motif known as the death fold and is related in sequence and structure to the death effector domain (DED) and the caspase recruitment domain (CARD), which work in similar pathways and show similar interaction properties.  DD bind each other forming oligomers.  Mammals have numerous and diverse DD-containing proteins.  Within these proteins, the DD domains can be found in combination with other domains, including: CARDs, DEDs, ankyrin repeats, caspase-like folds, kinase domains, leucine zippers, leucine-rich repeats (LRR), TIR domains, and ZU5 domains. Death's Domain is a book by Terry Pratchett and Stephen Briggs, and illustrated by Paul Kidby.  It is the fourth in the "Discworld Mapp" series, other publications of which include "The Streets of Ankh-Morpork, The Discworld Mapp" and "A Tourist Guide to Lancre."  It was first published in paperback by Corgi in 1999.  It was the second in the series to be illustrated by Kidby.  As with the other "mapps", the basic design and booklet were compiled by Pratchett and Briggs. The death fold is a tertiary structure motif commonly found in proteins involved in apoptosis or inflammation-related processes.  This motif is commonly found in domains that participate in protein–protein interactions leading to the formation of large functional complexes.  Examples of death fold domains include the death domain (DD), death effector domain (DED), Caspase Recruitment Domain (CARD), and pyrin domain (PYD). The Death Domain database is a secondary database of protein-protein interactions (PPI) of the death domain superfamily.  Members of this superfamily are key players in apoptosis, inflammation, necrosis, and immune cell signaling pathways.  Negative death domain superfamily-mediated signaling events result in various human diseases which include, cancers, neurodegenerative diseases, and immunological disorders.  Creating death domain databases are of particular interest to researchers in the biomedical field as it enables a further understanding of the molecular mechanisms involved in death domain interactions while also providing easy access to tools such as an interaction map that illustrates the protein-protein interaction network and information.  There is currently only one database that exclusively looks at death domains but there are other databases and resources that have information on this superfamily.  According to PubMed, this database has been cited by seven peer-reviewed articles to date because of its extensive and specific information on the death domains and their PPI summaries. The death-effector domain (DED) is a protein interaction domain found only in eukaryotes that regulates a variety of cellular signalling pathways.  The DED domain is found in inactive procaspases (cysteine proteases) and proteins that regulate caspase activation in the apoptosis cascade such as FAS-associating death domain-containing protein (FADD).  FADD recruits procaspase 8 and procaspase 10 into a death induced signaling complex (DISC).  This recruitment is mediated by a homotypic interaction between the procaspase DED and a second DED that is death effector domain in an adaptor protein that is directly associated with activated TNF receptors.  Complex formation allows proteolytic activation of procaspase into the active caspase form which results in the initiation of apoptosis (cell death).  Structurally the DED domain are a subclass of protein motif known as the death fold and contains 6 alpha helices, that closely resemble the structure of the Death domain(DD) A pyrin domain is a protein domain and a subclass of protein motif known as the death fold; it allows a pyrin domain containing protein to interact with other proteins that contain a pyrin domain.  It is also known as a PYD or PAAD/DAPIN domain, and is distantly evolutionarily related to the Death domain family of protein domains. Proteins containing a pyrin domain are frequently involved in biological processes called inflammation and apoptosis.  Proteins that possess a pyrin domain include intracellular microbial sensors called NOD-like receptors, and proteins associated with their function, such as PYCARD and certain fish caspases. Discworld is a comic fantasy book series written by the English author Terry Pratchett (1948–2015), set on the fictional Discworld, a flat disc balanced on the backs of four elephants which in turn stand on the back of a giant turtle, Great A'Tuin.  The books frequently parody or take inspiration from J. R. R. Tolkien, Robert E. Howard, H. P. Lovecraft, Charles Dickens, and William Shakespeare, as well as mythology, folklore and fairy tales, often using them for satirical parallels with current cultural, political, and scientific issues.  The series is popular, with more than 80 million books sold in 37 languages. Torii Tadanori (鳥居 忠則 , 1646 – September 6, 1689) was a Japanese "daimyō" of the early Edo period who ruled the Takatō Domain in Shinano Province (modern-day Nagano Prefecture).  Tadanori was the son of Torii Tadaharu, the previous lord.  He succeeded to family headship upon his father's death; however, he continued his father's draconian rule of the Takatō domain.  During the shogunate's investigation into a scandal involving Takatō retainer Takasaka Gonbei, Tadanori was ordered confined to his residence in Edo; he died during his confinement.  The Takatō domain was confiscated from the Torii family; however, as the Torii family was a famed fudai family dating back to Torii Mototada, Tadanori's heir Tadateru was granted four districts in Noto Province, and made the lord of the Shimomura Domain. Matsudaira Naritaka (松平 斉孝 ) (February 9, 1788 – February 26, 1838) was a Japanese daimyo of the late Edo period who ruled the Tsuyama Domain of Mimasaka Province.  Naritaka was the fourth son of Matsudaira Yasuchika, the fifth generation lord of Tsuyama; however, his brother Yasuharu succeeded to family headship first.  After Yasuharu's death, Naritaka became lord of Tsuyama; however, he was discontented with the aloof treatment which Tsuyama received from the Tokugawa house, despite its status as a "shinpan" (親藩; Tokugawa-branch) domain.  The domain had also been reduced from its onetime income of 100,000 koku.  Consequently, though he had many children of his own, he adopted the shogun Ienari's son Ginnosuke, in order to improve the relations between Tsuyama and the main Tokugawa family.  Upon Ginnosuke's adoption in 1817, 5,000 koku was added to the Tsuyama income, returning it to its previous 100,000 koku.  Naritaka resigned in the winter of 1831, and Ginnosuke, as Matsudaira Naritami, succeeded him.  Matsudaira Sadayasu, his son by birth, became lord of the Matsue Domain.
Answer: a flat disc balanced on the backs of four elephants which in turn stand on the back of a giant turtle