Lysozyme tertiary structure

FIGURE 5.32 The tertiary structures of heii egg white lysozyme and human o -lactal-bumin are very similar. (Adapted from Acharya, K K, ct at., 7996. Journal of Protein Chemistry 9 549-563 and Acharya, K R., ct at., 1997. Journal of Molecular Biology 221 571—581. 

Figure 2.10 Secondary and tertiary structure of the enzyme lysozyme, PDB 2C80. Visualized using Cambridge Soft Chem3D Ultra 10.0 with notations in ChemDraw Ultra 10.0. ChemDraw Ultra, version 10.0. (Printed with permission of CambridgeSoft...

One ionic bond that often helps establish tertiary structure is a disulfide bond between two cysteine side chain groups—for instance, in the enzyme lysozyme as shown in Figure 2.10. Lysozyme is not a metalloprotein, such as will be studied in this text, but it is a small enzyme and is illustrative of some secondary and tertiary structures found in the more complex molecules described in the following chapters. Lysozyme protects biological species from... 

In an earlier experiment, Jori et al. (14) reported that methionyl residues are important in maintaining the tertiary structure of lysozyme. The introduction of a polar center into the aliphatic side chain of methionine, as a consequence of the conversion of the thioether function to the sulfoxide, may bring about a structural change of the lysozyme molecule which, in turn, reduces the catalytic efficiency. When ozonized lysozyme was treated with 2-mercaptoethanol in an aqueous solution according to the procedure of Jori e al. (14), the enzyme did not show any increase in its activity. This may be explained in two ways. In one, such reactions are complicated by many side reactions, e.g. sulfhydryl-disulfide interchange, aggregation and precipitation of the modified enzyme (24-26). In the other, the failure to recover the activity of the enzyme may by associated with the extensive oxidation of other residues. 

T4 lysozyme 33,497 helix stability of 528, 529 hydrophobic core stability of 533, 544 Tanford j8 value 544, 555, 578, 582-Temperature jump 137, 138, 541 protein folding 593 Terminal transferase 408,410 Ternary complex 120 Tertiary structure 22 Theorell-Chance mechanism 120 Thermodynamic cycles 125-131 acid denaturation 516,517 alchemical steps 129 double mutant cycles 129-131, 594 mutant cycles 129 specificity 381, 383 Thermolysin 22, 30,483-486 Thiamine pyrophosphate 62, 83 - 84 Thionesters 478 Thiol proteases 473,482 TNfn3 domain O-value analysis 594 folding kinetics 552 Torsion angle 16-18 Tbs-L-phenylalanine chloromethyl ketone (TPCK) 278, 475 Transaldolase 79 Tyransducin-o 315-317 Transit time 123-125 Transition state 47-49 definition 55... 

The tertiary structure of native proteins is stabilized through hydrophobic interactions in the interior of the three-dimensional structure. The strongly hydrophobic conditions of RPC are known to unfold this conformation. With some species, e.g., with lysozyme, the unfolding is reversible. Here, even RPC does not produce permanently deactivated species but, in general, unfolding causes denaturation. 

The study by Determan et al. [224] focuses on the effects of polymer degradation products on the primary, secondary, and tertiary structure of TT, OVA, and lysozyme after incubation for 0 or 20 days in the presence of ester (lactic acid and glycolic acid) and anhydride [sebacic acid and l,6-bis(p-carboxyphenoxy)hexane] monomers. The structure and antigenicity or enzymatic activity of each protein in the presence of each monomer was quantified. SDS-PAGE, circular dichroism, and fluorescence spectroscopy were used to assess/evaluate the primary, secondary, and tertiary structures of the proteins, respectively. ELISA was used to measure changes in the antigenicity of TT and OVA and a fluorescence-based assay was used to determine the enzymatic activity of lysozyme. TT toxoid was found to be the most stable in the presence of anhydride monomers, while OVA was most stable in the... 

Fig. 7. The tertiary structure of (a) baboon a-lactalbumin and (b) domestic hen egg-white lysozyme. (Reproduced with permission from Acharya et ai, 1989 based on a program of J. P. Priestle.)...

A prerequisite for the catalytic function of an enzyme is its native tertiary structure which is determined by the number and sequence of amino acids (primary structure) forming the molecule. Favoured by hydrogen bonds, parts of the polypeptide chain exist in an a-helical or a (3-sheet structure (secondary structure). Most enzymes are globular proteins, the tertiary structure of which may be fixed by disulfide bonds between cysteine residues. A famous example is lysozyme (Fig. 20), consisting of 129 amino acids. A defined three-dimensional structure is... 

The determination of the tertiary structure of the hens egg white lysozyme, and the subsequent proposal that the side-chain carboxyhc acid group of Glu 35 act as a general acid, and the ionised side chain of Asp 52 acted to electrostatically stabilise an oxocarbonium ion intermediate, led to a search for a manifestation of these phenomena in model systems [6]. In the scramble electrostatic stabilisation was invoked where there was no compelling reason to distinguish it from ordinary nucleophilic participation. Thus, 3,5-dichlorophenolate departs from compound XXXII 100 times faster than from its p-isomer [94] a similar 22-fold acceleration of the ortho compared to the para isomer was observed with compound XXXIII. The rate acceleration in both cases was attributed to electrostatic stabihsation, but since the 3-methoxyphthalide was in both cases the product, it is not clear why humdrum neighbouring group participation was not invoked. 

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