Acylation protein stability

C-H Jt interaetions are moderate but nevertheless important interactions that contribute to protein stability (Brandi et al., 2001). Modeling studies illustrated in Eigure 2.9 suggest that F3.25(190) has a C-H jt interaction with the C5-C6 double bond in the AEA acyl chain. This interaction is consistent with a recent mutation study which showed that a E3.25(190). A mutation resulted in a 6-fold loss inaflinity for AEA [CBj WTKj = 0.3 pM(0.1-0.6) CBj E3.25A = 1.8 iM... 

In contrast, with penicillins, cephalosporins, and monobactams where the substituents are cis to each other across the C3 - C4 bond, clockwise rotation can occur without conflict with protein side chains, and will leave the path open for the water molecule to attack and hydrolyze the ester group in B (Scheme 10). Thus, czs-substituted monobactam, as well as penicillins and cephalosporins are rapidly hydrolyzed by class C enzymes (Scheme 10). If this rotation could be prevented by a suitable structural modification, the access of the water molecule to the ester bond will be blocked, which would result in increased stability of the acyl-enzyme complex. 

Although the stabilizing interactions between the amino acid side chains of PLC/j, and the choline headgroup are readily apparent in the PLC fc-phosphonate inhibitor complex, it is more difficult to identify contacts between the protein and the acyl chains of the inhibitor [45]. In part this is because thermal motion in the acyl side chains, especially the sn-1 chain, renders them somewhat disordered. Consequently, the measured distances between the side chain carbons... 

The hydrolysis of peptide bonds catalyzed by the serine proteases has been the reaction most extensively studied by low-temperature trapping experiments. The reasons for this preference are the ease of availability of substrates and purified enzymes, the stability of the proteins to extremes of pH, temperature, and organic solvent, and the existence of a well-characterized covalent acyl-enzyme intermediate. Both amides and esters are substrates for the serine proteases, and a number of chromo-phoric substrates have been synthesized to simplify assay by spectrophotometric techniques. 

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 ... 

Membranes are composed of lipids and proteins in varying combinations particular to each species, cell type, and organelle. The fluid mosaic model describes features common to all biological membranes. The lipid bilayer is the basic structural unit. Fatty acyl chains of phospholipids and the steroid nucleus of sterols are oriented toward the interior of the bilayer their hydrophobic interactions stabilize the bilayer but give it flexibility. 

The structure of spectrin and the location of spectrin in the cytoskeleton. (a) An a/3 dimer of spectrin. Both a and f3 subunits are extended structures consisting of end-to-end domains of 106 amino-acyl residues folded into three a helices the subunits twist about one another loosely as shown. (b) The erythrocyte membrane skeleton. Spectrin tetramers ((X2P2), shown in yellow, are linked to the cytoplasmic domain of the anion channel (blue) by the protein ankyrin (red), and to glycophorin and actin filaments by protein 4.1. This structure lends stability to the red cell membrane while maintaining sufficient flexibility to allow erythrocytes to withstand substantial shear forces in the peripheral circulation. 

Dasgupta P, Singh A, Mukherjee R (2002) N-terminal acylation of somatostatin analog with long chain fatty acids enhances its stability and anti-proliferative activity in human breast adenocarcinoma cells. Biol Pharm Bull 25 29-36 Delgado C, Francis GE, D. F (1992) The uses and properties of PEG-linked proteins. Crit Rev Ther Drug Carrier Syst 9 249-304... 

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