Noncovalent bonds membranes protein structure

Structure of membranes, biopolymers, and multimacromolecular assemblies because of actions on noncovalent bonds. Differtial alterations in the hydrophobic interactions within proteins [43-45], micelles, and lipids [46] are observed due to increased pressure. 

The formation of peptide bonds between amino acid residues, which is directed by mRNA and catalyzed by ribosomes, is at the heart of protein biosynthesis. However, a wide variety of other processes are also necessary for proteins to achieve their biological function(7, ). All polypeptides must undergo noncovalent changes, such as folding of the polypeptide chain, association with other subunits, and translocation across membranes. Many also undergo covalent modifications of both the peptide backbone and amino acid side chains. These covalent modifications can drastically affect both protein structure and function. 

N-Myristoylation is achieved by the covalent attachment of the 14-carbon saturated myristic acid (C14 0) to the N-terminal glycine residue of various proteins with formation of an irreversible amide bond (Table l). 10 This process is cotranslational and is catalyzed by a monomeric enzyme called jV-myri s toy 11ransferase. 24 Several proteins of diverse families, including tyrosine kinases of the Src family, the alanine-rich C kinase substrate (MARKS), the HIV Nef phosphoprotein, and the a-subunit of heterotrimeric G protein, carry a myr-istoylated N-terminal glycine residue which in some cases is in close proximity to a site that can be S-acylated with a fatty acid. Functional studies of these proteins have shown an important structural role for the myristoyl chain not only in terms of enhanced membrane affinity of the proteins, but also of stabilization of their three-dimensional structure in the cytosolic form. Once exposed, the myristoyl chain promotes membrane association of the protein. 5 The myristoyl moiety however, is not sufficiently hydrophobic to anchor the protein to the membrane permanently, 25,26 and in vivo this interaction is further modulated by a variety of switches that operate through covalent or noncovalent modifications of the protein. 4,5,27 In MARKS, for example, multiple phosphorylation of a positively charged domain moves the protein back to the cytosolic compartment due to the mutated electrostatic properties of the protein, a so-called myristoyl-electrostatic switch. 28 ... 

Figure 3.1 Macromolecular structures in biological molecules. Most biological macromolecules are composed of a limited number of building blocks joined by covalent bonds, as shown for deoxyribonucleic acid (A) and proteins (B). Membranes (C) are composed of a large diversity of molecules sharing similar physical properties that allow for noncovalent self-association.

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