Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.17 (lysozyme)
 21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Since elucidation of structure of deoxyribonucleic acid (DNA) as genetic material, it was established that DNA makes ribonucleic acid, which makes protein according to the original information given in DNA base as base sequences. From these basic idea of genetic flow system there was emerged the word "protein engineering". According to this principle, engineering of h-lysozyme, RNase H and their relevant proteins was described. A triosephosphate isomerase barrel type protein was designed and expressed.
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PMID:[From nucleic acids to proteins]. 190 4

The denaturant-dependence of the major, observable relaxation rates for folding (kobs) of ribonuclease HI from Escherichia coli (RNase H) and phage T4 lysozyme (T4L) reveal that, for both proteins, folding begins with the rapid and transient accumulation of intermediate species in a "burst phase" which precedes the rate-limiting formation of the native state; this is evidenced by a "rollover" in the folding limb of the rate profiles (kobs versus denaturant, or chevron plot). These rate profiles are most simply described by a three-state mechanism (unfolded-to-intermediate-to-native), which implies that the burst phase represents a transition between two distinct thermodynamic states. It is shown here that the equilibrium properties of these burst phase reactions can be equally well modeled by a mechanism involving a continuum of states where the free energy of each state is linearly related to its m-value (the parameter describing the linear relationship between free energy and denaturant). A numerical model is also developed to describe the time evolution of such a system, which exhibits nearly perfect exponential behavior. Both models emphasize how a continuum of states operating under a linear free energy relationship may behave like a two state system. Such a scheme finds experimental justification from an interpretation of recent native state hydrogen exchange data. The analytical model described for a continuum can account for the observed kinetic profiles of several other model proteins. The results, however, appear context specific, suggesting that burst phase reactions are not entirely random and non-specific. The results reported in this study have important implications for the concept of cooperativity in protein folding reactions.
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PMID:The cooperativity of burst phase reactions explored. 1054 95

We have used 2H-nmr to study backbone dynamics of the 2H-labeled, slowly exchanging amide sites of fully hydrated, crystalline hen egg white lysozyme. Order parameters are determined from the residual quadrupole coupling and values increase from S2 = 0.85 at 290 K to S2 = 0.94 at 200 K. Dynamical rates are determined from spin-lattice relaxation at three nmr frequencies (38.8, 61.5, and 76.7 MHz). The approach used here is thus distinct from solution nmr studies where dynamical amplitudes and rates are both determined from relaxation measurements. At temperatures below 250 K, relaxation is independent of the nmr frequency indicating that backbone motions are fast compared to the nmr frequencies. However, as the temperature is increased above 250 K, relaxation is significantly more efficient at the lowest frequency, which shows, in addition, the presence of motions that are slow compared to the nmr frequencies. Using the values of S2 determined from the residual quadrupole coupling and a model-free relaxation formalism that allows for fast and slow internal motions, we conclude that these slow motions have correlation times in the range of 0.1 to 1.0 microsecond and are effectively frozen out at 250 K where fast motions of the amide planes with approximately 15 ps effective correlation times and 9 degrees rms amplitudes dominate relaxation. The fast internal motions increase slightly in amplitude as the temperature rises toward 290 K, but the correlation time, as is also observed in solution nmr studies of RNase H, is approximately constant. These findings are consistent with hypotheses of dynamic glass transitions in hydrated proteins arising from temperature-dependent damping of harmonic modes of motion above the transition point.
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PMID:Backbone motions in a crystalline protein from field-dependent 2H-NMR relaxation and line-shape analysis. 1064 47

For a number of proteins, folding occurs via the rapid accumulation of secondary and tertiary structural features in a so-called burst phase, preceding the relatively slow, highly activated transition leading to the native state. A fundamental question is: do these burst phase reactions comprise two phase-separated thermodynamic states or a continuum of states? Ribonuclease HI (RNase H) from Escherichia coli and phage T4 lysozyme (T4L) both exhibit such a phenomenon. Native-state hydrogen exchange (NHX) data have been collected for these proteins, providing residue-specific free energies and m-values (a measure of hydrocarbon solvation) for the manifold of partially unfolded, exchange-competent forms that are accessible from the native state (DeltaG(sg) and m(sg), where the sg subscript denotes sub-global). There is good evidence that these parameters pertain to exchange-competent species comprising the burst phase observed in the global folding kinetics. We combine the results from the global folding kinetics of these proteins with a statistical analysis of their NHX parameters to determine if the distribution of experimental (m(sg), DeltaG(sg)) values derive from a mechanism where the burst phase is two-state. For RNase H, this analysis demonstrates that the burst phase of this protein is not two-state; the results imply a distribution of states, m and DeltaG exhibiting a linear functional relationship consistent with the global folding parameters. For T4L, it is difficult to distinguish the observed distribution of m(sg), DeltaG(sg) values from that expected for a mechanism where the burst phase is two-state. The results for RNase H* lend support for the idea that the burst phase reaction of this protein comprises a continuum of states. This has important implications for how we model the process of structural acquisition in protein folding reactions.
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PMID:A statistical appraisal of native state hydrogen exchange data: evidence for a burst phase continuum? 1090 74