Connexin 26
Connexins are membrane proteins which form intercellular channels responsible for the communication between plasma membranes, and allow transport of ions, signalling molecules and nutrients. These channels are referred to as gap junctions, its function determined by the type of connexin proteins that forms the channel as it affects the size and transport of certain molecules. In total there are 21 different connexin proteins. In particular the gap junction beta 2 (GJB2 gene), also known as connexin 26 creates gap junctions made specifically to pass potassium ions and other small cytoplasmic molecules to neighbouring cells in the cochlea. A mutation in this gene, or connexin 26 (Cx26), can cause a malfunction in the gap junctions
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The primary structure of a protein is its specific amino acid sequence. In connexin 26 in particular the amino acid sequence is: (MDWGTLQTILGGVNKHSTSIGKIWLTVLFIFRIMILVVAAKEVWGDEQADFVCNTLQPGCKNVCYDHYFPISHIRLWALQLIFVSTPALLVAMHVAYRRHEKKRKFIKGEIKSEFKDIEEIKTQKVRIEGSLWWTYTSSIFFRVIFEAAFMYVFYVMYDGFSMQRLVKCNAWPCPNTVDCFVSRPTEKTVFTVFMIAVSGICILLNVTELCYLLIRYCSGKSKKPV). Cx26 also contains the N-terminus, a free α-amino group ending of the amino acid chain sequence rather than with free carboxyl group.
In the secondary structure, the conformations of the proteins or amino acid chain depend on the hydrogen bonding between the molecules. Two main types of secondary structures are α-helices and the ß-sheets. In Cx26, the amino acid sequence forms into a α-helical domains. In the Cx26 protein there is also another secondary structure called 310 helix.
The Cx26's quaternary structure are made from Cx26 protomer which contains four transmembrane segments, noted as TM1, TM2, TM3, TM4, tw/lo extracellular loops (E1, E2), a cytoplasmic loop, a C-terminal segment and an N-terminal helix.
In the Cx26 protomer, the TM3 serves as the major pore helix causing the TM1 to narrow down into the short 310 helix. At the beginning of E1 there is a 310 helix and also a short α-helix in the half of the C-terminal. Combined, E1 and E2 have a short β-sheet, stretching over
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Researchers infected Sf9 insect cells with the baculovirus, grown at 27-28o after inserting human Cx26 DNA through a transfer vector. The Cx26 gap junction then, was first solubilised in dodecylmaltoside and then purified by cation exchange and size exclusion chromatography. After the purification came a series of centrifuging and supplementing of 50mg/L SeMet and 150 mg/L. Using PEG200 as precipitant, crystals were grown by the hanging-drop vapour diffusion method. After cultivating the crystals, the structure of Cx26 was depicted with the SIRAS (single isomorphous replacement with anomalous
The shape of the protein chains that produce the building blocks and other structures used in life is mostly determined by weak chemical bonds that are easily broken and remade. These chains can shorten, lengthen, and change shape in response to the input or withdrawal of energy. The changes in the chains alter the shape of the protein and can also alter its function or cause it to become either active or inactive. The ATP molecule can bond to one part of a... ... middle of paper ... ...
called an active site. This active site is made by a few of the amino
...s to interfere with bonding to the receptors. The final possibility uses CNP, which downregulates the activation in MAP kinase pathways in the chondrocytes (4).
(A) A monomer showing the central α-helix flanked by N-terminal and C-terminal regions. (B) Dimer of two monomers are coiled coil with a length of 48nm. (C) Assembly of antiparallel dimers forming a staggered tetramer. (D) Two tetramers are linked together. (E) The 10nm-intermediate filament is composed of twisted eight tetramers. Figure adapted from Alberts et al., 2008).
PVX forms small filamentous virions which have a deeply grooved surface [2]. The flexuous filaments consist of a single plus-strand genomic RNA coated with viral coat protein (CP). The helical structure has a pitch of 3.6nm and contains 8 7/8 CP subunits per turn [3]. The full-length filaments have a model length of 515nm with a diameter of 13nm [4].
problems within the specific ion channels known to cause the disease. The goal of the
From this point, vibration of the connective membrane (oval window) transforms mechanical motion into a pressure wave in fluid. This pressure wave enters and hence passes vibrations into the fluid filled structure called the cochlea. The cochlea contains two membranes and between these two membranes, are specialized neurons or receptors called hair cells. Once vibrations enter the cochlea, they cause the lower membrane (basilar membrane) to move in respect to the upper membrane (i.e. the tectorial membrane in which the hair cells are embedded). This movement bends the hair cells to cause receptor potentials in these cells which in turn cause the release of transmitter onto the neurons of the auditory nerve.
"The Species of the Secondary Protein Structure. Virtual Chembook - Elmhurst College. Retrieved July 25, 2008, from http://www.cd http://www.elmhurst.edu/chm/vchembook/566secprotein.html Silk Road Foundation. n.d. - n.d. - n.d.
contains three components. First it is constructed with a phosphorylated head group, then a three
Many proteins are the most prominent structural motif of the functional protein in its native conformation known as the alpha helix (Pauling et al. 1951). When a protein follows the wrong folding pathway, the protein misfolds and becomes a toxic configuration. When a protein becomes toxic, it obtains a motif known as the beta sheet. Although the beta sheet conformation also exists in many functional native proteins, the abnormal conformational change from alpha helix to beta sheet exposes
The birth of genetic engineering and recombinant DNA began in Stanford University, in the year 1970 (Hein). Biochemistry and medicine researchers were pursuing separate research pathways, yet these pathways converged to form what is now known as biotechnology (Hein). The biochemistry department was, at the time, focusing on an animal virus, and found a method of slicing DNA so cleanly that it would reform and go on to infect other cells. (Hein) The medical department focused on bacteria and developed a microscopic molecular messenger, that could not only carry a foreign “blueprint”, or message, but could also get the bacteria to read and copy the information. (Hein) One concept is needed to understand what happened at Stanford: how a bacterial “factory” turns “on” or “off”. (Hein) When a cell is dividing or producing a protein, it uses promoters (“on switches”) to start the process and terminators (“off switches”) to stop the process. (Hein) To form proteins, promoters and terminators are used to tell where the protein begins and where it ends. (Hein) In 1972 Herbert Boyer, a biochemist, provided Stanford with a bacterial enzyme called Eco R1. (Hein) This enzyme is used by bacteria to defend themselves against bacteriophages, or bacterial viruses. (Hein) The biochemistry department used this enzyme as a “molecular scalpel”, to cut a monkey virus called SV40. (Hein) What the Stanford researchers observed was that, when they did this, the virus reformed at the cleaved site in a circular manner. It later went on to infect other cells as if nothing had happened. (Hein) This proved that EcoR1 could cut the bonding sites on two different DNA strands, which could be combined using the “sticky ends” at the sites. (Hein). The contribution towards genetic engineering from the biochemistry department was the observations of EcoR1’s cleavage of
Moran, L.A. Horton, R.A. Scrimgeour, G. et al. (2014b) "Amino Acids and the Primary Structures of Proteins" In Principles of Biochemistry: Pearson New International Edition Fifth Edition ed. Edinburgh Gate, Harlow, Essex, CM20 2JE: Pearson Education Limited. pp. 94.
Some important AA sites within the protein sequence are: 431 – which is one amino acid in length, a proton donor and a binding site for thiamine pyrophosphate; 167 – which is one amino acid in length and a metal binding site; 197 – which is one amino acid in length and a binding site for, both, magnesium and thiamine pyrophosphate; 76 and 459 – which are, both, one amino acid in length and binding sites for thiamine pyrophosphate; 273 – which is one amino acid in length, a binding site for thiamine pyrophosphate and an essential site for catalytic activity; and 126 through 128 – which, altogether, comprise three amino acids in length and are the sites for nucleotide binding of thiamine pyrophosphate. The actual sequence’s chain begins at 2 and ends at 706 (Sakai et al, 1998); the first in the sequence (“1”) is removed as the methionine initiator. However, the “family tree”
1- ) Primary Structure is the sequence of a chain of amino acids. Proteins are formed from 20 different amino acids. Amino acid are composed of a carbon (α carbon) that bond to the hydrogen atom (H), a carboxyl group (-COOH), an amino group (-NH2) and a variable group, or R group. The primary structure is determined during translation. There are two tools uses to determine the primary structure; Edman degradation and mass spectrometry. Primary structure controls the secondary, tertiary and quaternary structures. It is also used to determine the molecular mass and isoelectric point.
A polypeptide chain is a series of amino acids that are joined by the peptide bonds. Each amino acid in a polypeptide chain is called a residue. It also has polarity because its ends are different. The backbone or main chain is the part of the polypeptide chain that is made up of a regularly repeating part and is rich with the potential for hydrogen-bonding. There is also a variable part, which comprises the distinct side chain. Each residue of the chain has a carbonyl group, which is good hydrogen-bond acceptor, and an NH group, which is a good hydrogen-bond donor. The groups interact with the functional groups of the side chains and each other to stabilize structures. Proteins are polypeptide chains that have 500 to 2,000 amino acid residues. Oligopeptides, or peptides, are made up of small numbers of amino acids. Each protein has a precisely defined, unique amino acid sequence, referred to as its primary structure. The amino acid sequences of proteins are determined by the nucleotide sequences of genes because nucleotides in DNA specify a complimentary sequence in RNA, which specifies the amino acid sequence. Amino acid sequences determine the 3D structures of proteins. An alteration in the amino acid sequence can produce disease and abnormal function. All of the different ways