The heptad repeat is an example of a structural motif that consists of a repeating pattern of seven amino acids: a b c d e f g H P P H C P C where H represents hydrophobic residues, C represents, typically, charged residues, and P represents polar (and, therefore, hydrophilic) residues. The positions of the heptad repeat are commonly denoted by the lowercase letters a through g. These motifs are the basis for most coiled coils and, in particular, leucine zippers, which have predominantly leucine in the d position of the heptad repeat.
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These 35 points form the surface S known as the Klein quadric. For each of the 28 points off S there are 6 lines through it which do not intersect S. As there are seven days in a week, the heptad is an important part of the solution: A heptad is determined by any two of its points. Each of the 28 points off S lies in two heptads.
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The standard Alphabody scaffold contains three α-helices, composed of four heptad repeats (stretches of 7 residues) each, connected via glycine/serine-rich linkers. The standard heptad sequence is "IAAIQKQ". Alanines are associated with α-helix formation, while isoleucines are known to induce coiled-coil formation. Specific residues on the A and C helices can be modified to bind targets, but only variants that retain thermostability are used for further research.
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An Alphabody scaffold variant with shorter linkers can be produced without the loss of thermostability. However, decreasing the number of heptad repeats per α-helix reduces the thermostability of the Alphabody by around 40 °C.
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Spectrin repeats are found in several proteins involved in cytoskeletal structure. These include spectrin, alpha-actinin, dystrophin and more recently the plakin family. The spectrin repeat forms a three-helix bundle. These conform to the rules of the heptad repeat.
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The structure of lamins is composed of three units that are common among intermediate filaments: a central α-helical rod domain containing heptad repeats surrounded by globular N and C-terminal domains. The N-terminal is shorter and located at the top (head) while the C-terminal is longer and located at the end (tail). Lamins have a unique structure of the heptad repeats that is continuous in nature and contains an additional six heptads. While the head domain of lamins is fairly consistent, the composition of the tail domain varies based on the type of lamin.
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There are 8 heptads. The projective linear group PGL(3,2) is isomorphic the alternating group on the 8 heptads. The schoolgirl problem consists in finding seven lines in the 5-space which do not intersect and such that any two lines always have a heptad in common.
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Gp41 has three prominent regions within the sequence: the ectodomain, the transmembrane domain, and the cytoplasmic domain. The ectodomain, which comprises residues 511-684, can be further broken down into the fusion peptide region (residues 512-527), the helical N-terminal heptad repeat (NHR) and C-terminal heptad repeat (CHR). In addition to these regions, there is also a loop region that contains disulfide bonds that stabilize the hairpin structure (the folded conformation of gp41) and a region called the membrane proximal external region (MPER) which contains kinks that are antigen target regions. The fusion peptide region is normally buried or hidden by the non-covalent interactions between gp120 and gp41, at a point which looks torus-like.
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Yazidi men Yazidis, who have much in common with the followers of Yarsanism, state that the world created by God was at first a pearl. It remained in this very small and enclosed state for some time (often a magic number such as forty or forty thousand years) before being remade in its current state. During this period the Heptad were called into existence, God made a covenant with them and entrusted the world to them. Besides Tawûsê Melek, members of the Heptad (the Seven), who were called into existence by God at the beginning of all things, include Sheikh ‘Adī ibn Musāfir al-Umawī (Şêx Adî), his companion Şêx Hasan and a group known as the Four Mysteries: Shamsadin, Fakhradin, Sajadin and Naserdin.
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Sapthamatha are a group of seven Hindu goddesses who are always depicted together.Kinsley, p.151 Since they are usually depicted as a heptad, they are called Saptamatrikas (Sanskrit: , , "seven mothers"): Brahmani, Vaishnavi, Maheshvari, Indrani, Kaumari, Varahi and Chamunda or Narasimhi. In Tamil Nadu temples, the sapthamtha is rarely represented in the dancing form compared to their northern counterparts.
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Zebende, G. and Moret, M. Phys. Rev. E 75, 011920 (2007) He has proved the superiority of this scale against other scales for numerous (especially heptad) transmembrane proteins. Using profile smoothing methods he has found otherwise inaccessible correlations between protein properties and thousands of amino acid sequences, based on homologous globular features of water film packages.
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PMS2 has been shown to interact with MLH1 by forming the heterodimer MutLα. There is competition between MLH3, PMS1, and PMS2 for the interacting domain on MLH1, which is located in residues 492-742. The interacting domains in PMS2 have heptad repeats that are characteristic of leucine zipper proteins. MLH1 interacts with PMS2 at residues 506-756.
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Furthermore, these conformational changes are irreversible processes. HIV-1 fusion process. It involves both subunits of the envelope spike complex. Notably, gp41 is shown in green with its transmembrane region buried in the virion membrane, both segments of heptad repeats (CHR closer to the virus and NHR closer to the host cell) before and after conformational changes, and the N-terminal end of the ectodomain in gray.
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Tenascin C is an oligomeric glycoprotein composed of individual polypeptides with molecular weights ranging from 180 to ~300kDa. The Tenascin family of proteins shares a similar structural pattern. These similar modules include heptad repeats, EGF-like repeats, fibronectin type III domains, and a C-terminal globular domain shared with fibrinogens. These protein modules are lined up like beads on a string and give rise to long and extended molecules.
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Studies in the hematopoietic system disclosed that during endothelial to hematopoietic stem cell transition, Gpr56 is a transcriptional target of the heptad complex of hematopoietic transcription factors, and is required for hematopoietic cluster formation. Recently, two studies showed that GPR56, is a cell autonomous regulator of oligodendrocyte development through Gα12/13 proteins and Rho activation. Della Chiesa et al. demonstrate that GPR56 is expressed on CD56dull natural killer (NK) cells.
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The most significant sequence similarities to this 54-amino acid region are from a motif found in the heavy chains of myosins from different organisms. A comparison of segment II with the vertebrate myosin heavy chains reveals that it is homologous to a myosin peptide in the hinge region linking the S2 and LMM domains. Segment II also contains heptad repeats which are characteristic of the myosin tail alpha-helical coiled-coils.
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Hindus and Theosophists call it Para Brahman (Parabrahm). Formless Parabrahm is said to periodically emanate Logoi, which are hence not causeless, but are non-eternal except in cycles of emanation, existence, pralaya (dissolution). In each cycle, causeless cause causes the Logoic Monad to move into action, which develops into the Logoic triad/triple manifestation, and the heptad (i.e. seven; prajapatis (Devas) or Elohim) which continue the cosmic chain of cause and effect.
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This protein has a domain of unknown function (DUF) 3496, which has been conserved in eukaryotes. The DUF3496 domain is found from amino acids 547-622. CCDC144A, an alias of this gene, indicates that there should be a coiled coil domain within the protein. Coiled coils are structural motifs in proteins in which 2 more alpha helices are coiled together, and they usually contain a heptad repeat, hxxhcxc, or hydrophobic (h) and charge (c) amino acid residues.
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This complex is relatively stable, and can undergo multiple rounds of transcription initiation. After the binding of TFIIB and TFIID, Pol II the rest of the GTFs can assemble. This assembly is marked by the post-translational modification (typically phosphorylation) of the C-terminal domain (CTD) of Pol II through a number of kinases. The CTD is a large, unstructured domain extending from the RbpI subunit of Pol II, and consists of many repeats of the heptad sequence YSPTSPS.
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The KRAB domain had initially been identified in 1988 as a periodic array of leucine residues separated by six amino acids 5’ to the zinc finger region of KOX1/ZNF10 coined heptad repeat of leucines (also known as a leucine zipper) . Later, this domain was named in association with the C2H2-Zinc finger proteins Krüppel associated box (KRAB). The KRAB domain is confined to genomes from tetrapod organisms. The KRAB containing C2H2-ZNF genes constitute the largest sub-family of zinc finger genes.
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In the second half of the 19th century, Martin Haug proposed that Zoroaster himself had viewed the Amesha Spenta as merely philosophical abstractions and that a personification of the heptad was really a later corruption. The Parsis of Bombay gratefully accepted Haug's premise as a defense against the Christian missionaries and subsequently disseminated the idea as a Parsi interpretation, which corroborated Haug's theory. The "continuing monotheism" principle eventually became so popular that it is now almost universally accepted as doctrine.
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IF central rods contain heptad repeats (repeating seven residue patterns) of hydrophobic resides that allow two different IF proteins to intertwine into a coiled-coil formation via hydrophobic interactions. These heterodimers are formed between specific pairs of type I (acidic) and type II (basic) keratin. K5, a type II keratin, pairs with the type I keratin K14. The coiled-coil dimers undergo stepwise assembly and combine in an antiparallel manner, forming end-to-end interactions with other coiled-coils to form large 10 nm intermediate filaments.
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The hydrophilic side of the helix interacts with the water in the solvent. Leucine zipper motifs are considered a subtype of coiled coils, which are built by two or more alpha helices that are wound around each other to form a supercoil. Coiled coils contain 3- and 4-residue repeats whose hydrophobicity pattern and residue composition is compatible with the structure of amphipathic alpha-helices. The alternating three- and four-residue sequence elements constitute heptad repeats in which the amino acids are designated from a’ to g’.
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Islam regards Gabriel (Jibril) as an archangel sent by God to various prophets, including Muhammad. The first five verses of the Al-Alaq, the 96th chapter of the Quran, is believed by Muslims to have been the first verses revealed by Jibril to Muhammad. The Latter Day Saints hold that the angel Gabriel is the same individual as the prophet Noah in his mortal ministry. Yazidis consider Gabriel one of the Seven Mysteries, the heptad to which God entrusted the world and sometimes identified with Melek Taus.
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The exact meaning of the allegorical women's role, behaviour, interrelation and color-coding remains a matter of literary interpretation. Later, in the High Middle Ages, some authors opposed the seven virtues (cardinal plus theological) to the seven capital sins. However, “treatises exclusively concentrating on both septenaries are actually quite rare.” and “examples of late medieval catalogues of virtues and vices which extend or upset the double heptad can be easily multiplied.” And there are problems with this parallelism. Fresco with allegories of the four cardinal virtues in the ‘’Assunta’’ church in Manerba del Garda.
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FAM167A has a leucine zipper as part of its secondary structure as noted by the four heptad leucine repeat regions shown in SAPS. The leucine zipper is a portion of the DUF domain. Predictions of the secondary structure for the FAM167A protein are mostly that it is made of alpha helices and coiled coils, which would be reasonable as there is a coiled coil domain. The C-terminus end of DUF3259 is generally agreed upon in the PELE program to be a region of potential beta sheets and coiled coils.
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Yazidism is a monotheistic faith based on belief in one God, who created the world and entrusted it into the care of a Heptad of seven Holy Beings, often known as Angels or heft sirr (the Seven Mysteries).Adam Valen Levinson The Abu Dhabi Bar Mitzvah: Fear and Love in the Modern Middle East W. W. Norton & Company 2017 Preeminent among these is Tawûsê Melek (also known as "Melek Taus"), the Peacock Angel. Traditionally, Yazidis who marry non-Yazidis are considered to have converted to the religion of their spouse.
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This work has also been incorporated as one of the foretales in Kinsella's translation of The Táin., also endnotes. This editorial decision is potentially confusing, since for the Tain Bo Cuailnge proper, he uses the first recension and not the Book of Leinster version. The work also contains interesting passage of hyperboles regarding the heptad of Fergus (), omitted by Kinsella, which states how Fergus had the appetite of seven men, a libido that could only be satisfied by seven women in the absence of his wife Flidas, and that the size of his phallus measured seven fists.
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In rare cases, individuals may have a mutation in the CCR5 delta gene which results in a nonfunctional CCR5 co-receptor and in turn, a means of resistance or slow progression of the disease. However, as mentioned previously, this can be overcome if an HIV variant that targets CXCR4 becomes dominant. To prevent fusion of the virus with the host membrane, enfuvirtide can be used. Enfuvirtide is a peptide drug that must be injected and acts by interacting with the N-terminal heptad repeat of gp41 of HIV to form an inactive hetero six-helix bundle, therefore preventing infection of host cells.
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Syncytin-1 shares many structural elements with class I retroviral glycoproteins (such as, Murine Leukemia Virus gp, Ebolavirus gp, and HIV gp120, gp41). It is composed of a surface subunit (SU) and transmembrane subunit (TM), separated by a furin cleavage site. The two subunits form a heterodimer and are likely linked by a disulfide bond between two conserved cysteine rich motifs: CXXC in SU and CX6CC in TM. This heterodimer likely forms a homotrimer at the cell surface. Syncytin-1 TM contains the fusion peptide, and two heptad repeats separated by a chain reversal region common to class I retroviral glycoproteins.
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TFIIH, the helicase that remains associated with Pol II throughout transcription, also contains a subunit with kinase activity which will phosphorylate the serines 5 in the heptad sequence. Similarly, both CDK8 (a subunit of the massive multiprotein Mediator complex) and CDK9 (a subunit of the p-TEFb elongation factor), have kinase activity towards other residues on the CTD. These phosphorylation events promote the transcription process and serve as sites of recruitment for mRNA processing machinery. All three of these kinases respond to upstream signals, and failure to phosphorylate the CTD can lead to a stalled polymerase at the promoter.
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Cells containing only RNAPII with none or only up to one-third of its repeats are inviable. The CTD is an extension appended to the C terminus of RPB1, the largest subunit of RNA polymerase II. It serves as a flexible binding scaffold for numerous nuclear factors, determined by the phosphorylation patterns on the CTD repeats. Each repeat contains an evolutionary conserved and repeated heptapeptide, Tyr1-Ser2-Pro3-Thr4-Ser5-Pro6-Ser7, which is subjected to reversible phosphorylations during each transcription cycle. This domain is inherently unstructured yet evolutionarily conserved, and in eukaryotes it comprises from 25 to 52 tandem copies of the consensus repeat heptad.
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In stories with eschatological significance, Sraosha (Sarosh), Mithra (Mihr), and Rashnu (Rashn) are guardians of the Chinvat bridge, the bridge of the separator, across which all souls must pass. Further, what the calendrical dedications had begun, the tradition completed: at the top of the hierarchy was Ahura Mazda, who was supported by the great heptad of Amesha Spentas (Ameshaspands/Mahraspands), through which the Creator realized ("created with his thought") the manifest universe. The Amesha Spentas in turn had hamkars, "assistants" or "cooperators", each a caretaker of one facet of creation. In both tradition and scripture, the terms 'Amesha Spenta' and 'yazata' are sometimes used interchangeably.
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Coiled-coil α helices are highly stable forms in which two or more helices wrap around each other in a "supercoil" structure. Coiled coils contain a highly characteristic sequence motif known as a heptad repeat, in which the motif repeats itself every seven residues along the sequence (amino acid residues, not DNA base-pairs). The first and especially the fourth residues (known as the a and d positions) are almost always hydrophobic; the fourth residue is typically leucine this gives rise to the name of the structural motif called a leucine zipper, which is a type of coiled-coil. These hydrophobic residues pack together in the interior of the helix bundle.
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The motor domain, which is organized into four subdomains (SH3-like motif, the upper and the lower 50kDa subdomains, and the converter region) connected by flexible linkers, interacts with filamentous actin to generate force through magnesium-dependent hydrolysis of ATP. The neck acts as a lever arm that amplifies the movement produced by conformational changes of the motor domain, and is the binding site for the light chains through two IQ motifs. The tail domain is fundamental for both dimerization of the heavy chains and formation of NM IIA functional filaments. Two heavy chains dimerize through the tail domain forming a long alpha-helical coiled-coil rod composed of typical heptad repeats.
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In Yazdâni theologies, an absolute pantheistic force (Hâk or Haqq) encompasses the whole universe. It binds together the cosmos with its essence, and has entrused the universe the heft sirr (the "Heptad", "Seven Mysteries", "Seven Angels"), who sustain universal life and can incarnate in persons, bâbâ ("Gates" or "Avatar").Kurdistanica – Encyclopaedia of Kurdistan: Cult of Angels These seven emanations are comparable to the seven Anunnaki aspects of Anu of ancient Mesopotamian theology, and they include Melek Taus (the "Peacock Angel" or "King"), who is the same as the ancient god Dumuzi son of Enki and the main deity in Yazidi theology, and Shaykh Shams al-Din, "the sun of the faith", who is Mithra.Bidlisi, Izady. 2000. p.
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BLNK consists of a N-terminal leucine zipper motif followed by an "acidic" region, a proline-rich region, and a C-terminal SH2 domain. The leucine zipper motif allows BLNK to localise to the plasma membrane, presumably by coiled-coil interactions with a membrane protein. This leucine zipper motif distinguishes BLNK from its paralogue SLP-76 which, although having an N-terminal heptad-like organisation of leucine and isoleucine residues, has not been experimentally shown to have this motif. Recruitment of BLNK to the plasma membrane is also achieved by binding of the SH2 domain of BLNK to a non-ITAM phospho-tyrosine on Igα, a part of the B cell receptor complex.
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P62 is a serine/threonine rich protein of ~520 amino acids, with tetrapeptide repeats on the amino terminus and a series of alpha- helical regions with hydrophobic heptad repeats forming beta-propeller domain. P62 assembles into a complex containing 3 addition proteins, p60, p54 and p45 forming the p62 complex of ~235 kDa. O-GlcNAcylation appears to be involved in the assembly and disassembly of p62 into higher order complexes, and a serine/threonine rich linker region between Ser270 to Thr294 appear to be regulatory. The p62 complex is localized to both the nucleoplasmic and cytoplasmic sides of the pore complex and the relative diameter of p62 complex relative to the nuclear pore complex suggests it interacts in pore gating.
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While residues in positions a and d are generally hydrophobic and form a zigzag pattern of knobs and holes that interlock with a similar pattern on another strand to form a tight- fitting hydrophobic core, residues in positions e and g are charged residues contributing to the electrostatic interaction. In the case of leucine zippers, leucines are predominant at the d position of the heptad repeat. These residues pack against each other every second turn of the alpha-helices, and the hydrophobic region between two helices is completed by residues at the a positions, which are also frequently hydrophobic. They are referred to as coiled coils unless they are proven to be important for protein function. If that is the case, then they are annotated in the “domain” subsection, which would be the bZIP domain.
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Replacement of the transmembrane domain with lipid anchors leads to an intermediate stage of membrane fusion where only the two contacting leaflets fuse and not the two distal leaflets of the two membrane bilayer. Although SNAREs vary considerably in structure and size, they all share a segment in their cytosolic domain called a SNARE motif that consists of 60-70 amino acids and contains heptad repeats that have the ability to form coiled-coil structures. V- and t-SNAREs are capable of reversible assembly into tight, four-helix bundles called "trans"-SNARE complexes. In synaptic vesicles, the readily-formed metastable "trans" complexes are composed of three SNAREs: syntaxin 1 and SNAP-25 resident in cell membrane and synaptobrevin (also referred to as vesicle- associated membrane protein or VAMP) anchored in the vesicle membrane.
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In particular, the relationship between Ahura Mazda and Spenta Mainyu is multifaceted and complex and "as hard to define as that of Yahweh and the Holy Spirit in Judaism and Christianity.". A veneration for the Amesha Spenta through the living world is still present in modern Zoroastrian tradition and is evident in every religious ceremony, when each of the Amesha Spenta is visibly represented by objects of which they are the guardians. In addition, the first seven days of the month of the Zoroastrian calendar are dedicated to the great heptad and to creation, acknowledging the preeminence of the Amesha Spenta and so ensuring the inculcation of their doctrine. Ethical and ontological dualism in the same entity "accounts for the difficulty which some aspects of the doctrine have presented for Western scholars".
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The linker becomes bent and shifts from AAA5 to AAA2 while remaining bound to AAA1. One attached alpha-helix from the stalk is pulled by the buttress, sliding the helix half a heptad repeat relative to its coilled- coil partner, and kinking the stalk. As a result, the MTBD of dynein enters a low-affinity state, allowing the motor to move to new binding sites. Following hydrolysis of ATP, the stalk rotates, moving dynein further along the MT. Upon the release of the phosphate, the MTBD returns to a high affinity state and rebinds the MT, triggering the power stroke. The linker returns to a straight conformation and swings back to AAA5 from AAA2 and creates a lever-action, producing the greatest displacement of dynein achieved by the power stroke The cycle concludes with the release of ADP, which returns the AAA domain ring back to the “open” configuration.
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Besides that, Ka'ba-ye Zartosht is a near to the mausoleums that were built at the same time; and all of them were later separated from the other parts of Naqsh-e Rustam by a chain of fortifications, indicating that they were all originally the same type and had similar applications. In other words, all of them, including they very Ka'ba-ye Zartosht, were mausoleums of Achaemenid grandees. Some other reasons can be stated for Ka'ba- ye Zartosht being a mausoleum; one is the triad and heptad units that are seen in the Achaemenid mausoleums. For example, the three-tomb chambers of the mausoleums connect them to making Ka'ba-ye Zartosht three-floor and its platform having three stairs; and the seven hatches of each floor of the structure remarks the Seven Persian Noblemen on the mausoleums and the Tomb of Cyrus having seven floors.
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