The Importance Of Proteins

The chaperones have the main role of ensuring proper folding. When a chaperone protein becomes toxic, major changes in the conformation occur as the alpha helix becomes beta pleated sheets. The sheets now expose the hydrophobic amino acid and aggregation, or clumping together of sheets occurs (Borges, 2014).

is loss of its structure. This occurs when the ionics and hydrogens bonds of the protein

A protein has multiple existing structures, these are the primary, secondary, tertiary and quaternary structures which occur progressively. A protein is essentially a sequence of amino acids which are bonded adjacently, and interact with one another in various ways depending on the R group that the amino acid contains. There are 20 different amino acids which are able to be arranged in any given order, thus giving rise to a potential 2.433x1018 (4.s.f) different combinations, and therefore interactions between the various amino acids.

Since the side chains are bonded to ions in solution, they are unavailable to bond with each other. This lack of bonding amongst the side chains effects the tertiary structures of the protein, changing its shape. The tertiary structure is important because for an enzyme to work, it must have a very specific shape to fit, lock and key style, onto the substrate. As the substrate and enzyme bind the shape of the substrate molecule slightly bends. This strains the bonds of the substrate, allowing them to be broken easy.

Proteins are primarily considered to have one primary function to serve its role in an organism, however studies have observed to have multiple functioning proteins known as moonlighting proteins (Khan et al. 2014). Moonlighting proteins along with primary functions, have secondary functions that are not related to the primary function and does not correlate to the primary or other functions (Khan et al. 2014). The multifunctional proteins play essential roles in carrying out biochemical functions which aids in the cell growth but are not caused by gene fusion and multiple RNA splice variants (Amblee et al. 2015). The discovery of moonlighting proteins was first discovered by Piatigorsky and Wistow while observing crystallins (Khan et al. 2014). Crystallins, are structural proteins that are found in the eye lens that exhibit enzymatic activity to make the lens itself (Khan et al. 2014). Crystallin has a primary function to help form the lens of the eye by acting as a structural protein (Amblee et al. 2015). Besides enzymatic activity, crystallin was observed in other mammals to have secondary functions such as metabolic functions which are helpful in prokaryotic (Khan et al 2014). Most moonlighting proteins are characterized as cytosolic enzymes and chaperons, or in other words helping proteins (Amblee et al 2015). The multifunctional proteins or moonlighting proteins can also be identified as receptors, channel proteins and ribosomal proteins (Khan et al. 2014). Due to the

Chaperones are proteins that ensure the correct folding of the CFTR within the endoplasmic reticulum. Hsp70 is an important cytosolic chaperone that complexes with CFTR and reduces aggregation [5]. The CFTR passes through the endoplasmic reticulum-associated degradation (ERAD) after folding in the ER. This quality control system involves the ubiquitin proteasome system (UPS) for which CFTR is a substrate [16]. If a protein is molded and targeted for degradation, then ubiquitin will covalently attach to lysine residues on the CFTR. Three enzymes are required for the process of ubiquitylation: E1 ubiquitin activating enzymes, E2 ubiquitin conjugating enzymes, and E3 ubiquitin protein ligases. E1 enzymes are activated through hydrolysis of ATP, which creates an activated ubiquitin that is transferred to an E2 active site. The activated ubiquitin is then covalently bound to a lysine on the protein by an E3 ligase. A polyubiquitin chain is then formed as ubiquitin molecules link together, and if there are four or more then the misfolded CFTR chain is removed form the ER membrane and targeted for degradation by the 26S proteasome

Proteins are biological macromolecules made from smaller building units called amino acids. There are 20 natural occurring amino acids which can combine in various ways to form a polypeptide. There are four distinctive levels of protein structure: primary, secondary, tertiary and quaternary. The primary structure of a protein is important in determining the final three dimensional structure and hence the role and function of a particular protein, both in the human body and in life around us. The secondary structure of a protein can fall into two major categories; α-helices or β-sheets, other variants also exist such as β-turns {{20 Brändén, Carl-Ivar, 1934- 1991}}. The precise folding or these secondary structures into a three dimensional shape is known as the tertiary structure of a protein and multiple polypeptides bound together via covalent and non-covalent bonds forms the complex quaternary structure of a protein.

There may also be sections where the secondary structure is neither helix nor sheet. Then the structure is called a random structure, indicating that it folds in random directions. The amino acids in an alpha helix are arranged in a right-handed helical structure resembling a spring. The alpha helix is the most common form of regular secondary structure in proteins. The beta-sheet is the second form of regular secondary structure in proteins consisting of beta strands connected laterally by three or more hydrogen bonds, forming a generally twisted, pleated sheet. The beta-sheet is sometimes called the beta pleated sheet since sequential neighboring atoms are alternately above and below the plane of the sheet giving a pleated appearance. Turns are the third of the three "classical" secondary structures that serve to reverse the direction of the polypeptide chain. They are located primarily on the protein surface and accordingly contain polar and charged residues. However, they are not very common in discussions of protein structure today.

The dexamethasone binding pocket of GR LBD consists of 3, 4, 5, 6, 7 and 10 helices as well as AF-2 helix. Within the crystals, dexamethasone shows a high affinity binding to the protein binding pocket [7, 1]. This high affinity binding is explained by the ability of dexamethasone to form both hydrophobic as well as hydrophilic interactions. Each atom of dexamethasone interacts with at least one of the hydrophobic residues from the GR LBD binding core. The hydrophilic interactions is formed by hydrogen bonds between the hydrophilic groups

The Functions of Proteins Introduction Protein accounts for about three-fourths of the dry matter in human tissues other than fat and bone. It is a major structural component of hair, skin, nails, connective tissues, and body organs. It is required for practically every essential function in the body. Proteins are made from the following elements; carbon, hydrogen, oxygen, nitrogen and often sulphur and phosphorus.

Bettelheim, Brown, Campbell and Farrell assert that polypeptide chains do not extend in straight lines but rather they fold in various ways and give rise to a large number of three-dimensional structures (594). This folding or conformation of amino acids in the localized regions of the polypeptide chains defines the secondary structure of proteins. The main force responsible for the secondary structure is the non-covalent

The endoplasmic reticulum (ER) is an essential organelle that is a major place for the biogenesis of cellular components including proteins, lipids, and carbohydrates and internal calcium storage. ER is primarily responsible for protein translocation, protein folding and protein post modification. Proper folding of protein in the ER is accomplished with the aid of ER resident proteins or enzymes such as chaperones. Binding of chaperones to

Due to the HEPN domains property of dimerizing, sacsin’s interaction with JIP3 may not occur exclusively though the HEPN domain in the absence of full-length sacsin. A mutated construct of HEPN called ARSACS Asn-4549 can disrupt HEPN dimerization due to the replacement of an asparagine with aspartic acid in the α4-α5 loop near the edge of the HEPN dimer interface2. Performing a pulldown assay with a mutated HEPN construct that retains the property of JIP3 binding, but is unable to dimerize would indicate that HEPN interacts with JIP3. However, this construct was found to destabilize HEPN folding through the loss of two polar contacts and the introduction of a charge at the dimer interface. Furthermore, the expression of this mutant HEPN domain in a bacterial system results in an insoluble protein which is unable to fold correctly and dimerize 2. Therefore, cloning a mutant HEPN construct, which is unable to dimerize would disrupt the protein’s tertiary structure, and a pulldown assay with this construct would likely be inefficient due to insolubility. Further experiments must be performed using a brain lysate from sacsin KO mice in a JIP3 pulldown assay to examine the role of HEPN dimerization in JIP3 binding.

These new formations are held together by hydrogen bonds. The third level is the tertiary structure. The tertiary structure of a protein is a contorted secondary structure being twisted and folded all out of shape to form a 3-d complex. The type of bonding that holds these formations together are weak interactions such as hydrophilic, hydrophobic, ionic, and hydrogen bonds. These bonds are individually weak, but collectively strong. The forth level, which completes a protein, is quaternary structure, which occurs when two or more tertiary structures are joined together by polypeptide bonds.

Molecular chaperones stabilize unfolded or misfolded proteins until native conformations have been obtained to promote cell survival during and after stress conditions. They do not change or add to the folding principles encoded by a protein because polypeptide chains inherently carry within them all the information that is necessary for achieving the native state of a protein. Instead, they optimize the folding process by stabilizing folding intermediates and are involved in every aspect of proteome maintenance including de novo folding, refolding of stress-induced misfolded proteins, and targeting proteins for degradation (Hartl 2009, Hartl 2011). Chaperones, many of which are induced or upregulated only during stress conditions, work in cooperative networks when protein-aggregate concentration