Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.31.1 (micrococcal nuclease)
 2,818 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Until recently, the energetics of protein-folding intermediates eluded direct measurement by high-sensitivity microcalorimetric techniques. But during the past year, the direct measurement of thermodynamic parameters for folding intermediates of alpha-lactalbumin, apomyoglobin, cytochrome c, and staphylococcal nuclease has provided new insights on the nature of the forces involved in the stabilization of nascent protein structures. In this review, I summarize those results and discuss the structural implications of the observed thermodynamic behavior.
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PMID:Thermodynamics of partly folded intermediates in proteins. 766 12

We have analyzed the effect of the chaperonin GroEL on the refolding kinetics of staphylococcal nuclease and its three mutants by stopped-flow fluorescence measurements. It was found that a transient folding intermediate of staphylococcal nuclease was tightly bound to GroEL and refolded in the GroEL-bound state without releasing the non-native protein in solution, and the refolding rate in the GroEL-bound state was 0.01 s-1. The GroEL-affected refolding of the nuclease appears to be in decided contrast to that of apo-alpha-lactalbumin reported in our previous study, wherein alpha-lactalbumin was shown to be more weakly bound by GroEL and to refold in the free state in solution. In spite of the apparent difference between the proteins, the GroEL-affected refolding reactions of both the proteins can be represented by a common unified reaction scheme. On the basis of this scheme, the binding constant between the nuclease intermediate and GroEL was estimated to be larger than 10(9) M-1. The stoichiometry of binding of the nuclease and its mutants to GroEL was found to be two (nuclease/GroEL 14-mer). The increase in ionic strength resulted in a weakening of the interaction between the nuclease and GroEL, which was attributed to a weakening of the electrostatic attraction between the two proteins as a result of electrostatic screening by ions. Although ATP was found to accelerate the GroEL-affected refolding of the nuclease, the refolding rate was still far from the rate of the free refolding. The free refolding behavior of the nuclease and its mutants was restored in the presence of the cochaperonin GroES and ATP.
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PMID:Refolding kinetics of staphylococcal nuclease and its mutants in the presence of the chaperonin GroEL. 953 91

Molten globules are partially structured protein folding intermediates that adopt a native-like overall backbone topology in the absence of extensive detectable tertiary interactions. It is important to determine the extent of specific tertiary structure present in molten globules and to understand the role of specific side-chain packing in stabilizing and specifying molten-globule structure. Previous studies indicate that a small degree of specific side-chain packing stabilizes the structures of the cytochrome c, apomyoglobin, and staphylococcal nuclease molten globules. Here we investigate the extent of specific side-chain packing in the molten globule of alpha-lactalbumin (alpha-LA), a highly fluctuating, non-cooperatively formed molten globule. By analyzing a set of point mutations in the helical domain of alpha-LA, we have identified a stabilizing hydrophobic core. Moreover, this core corresponds to a previously identified structural subdomain and likely contains some native-like packing interactions. Our results suggest that native-like packing of core amino acids helps stabilize molten globules and that some specific interactions can exist in even highly dynamic, fluctuating species.
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PMID:A specific hydrophobic core in the alpha-lactalbumin molten globule. 965 40