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)

This paper reports the results of numerous biochemical analyses which indicate that the "high mobility group" proteins (HMGs) of mouse and bovine cells are bona fide glycoproteins and can, in addition, be modified by poly(ADP-ribose) addition in vitro. The sugars N-acetylglucosamine, mannose, galactose, glucose, fucose, and one unknown sugar (possibly xylose) have been identified in purified preparations of HMGs 14 and 17. Furthermore, the fucose-specific lectin Ulex europeus agglutinin I bound both to the isolated HMGs and to monomer nucleosomes containing HMGs released from "active chromatin" by micrococcal nuclease digestion. Selective alkaline borohydride reductive cleavages of the HMGs suggested that the oligosaccharide prosthetic groups are primarily bound to these proteins by N-glycosidic linkages. The unexpected finding that the HMGs contain covalently bound complex carbohydrate moieties allows for a potentially great amount of variability and specificity in these proteins that may have important biological implications.
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PMID:Carbohydrate modifications of the high mobility group proteins. 645 17

The application of hydrostatic pressure to aqueous protein solutions results in the unfolding of the protein structure because the protein-solvent system volume is smaller for the unfolded state. Contributions to this decrease in volume upon unfolding (delta Vu) derive from altered interactions of the protein with solvent and are presumed to include electrostriction of charged residues, elimination of packing defects, and hydration of hydrophobic surfaces upon unfolding. If the contribution of hydrophobic surface area solvation to the observed volume change of unfolding were large and negative, as is generally assumed, then one would expect to find a correlation between the amount of surface area exposed on unfolding, delta A(u), and the volume change, delta Vu. In order to test this correlation, we have determined delta Vu for two mutants of staphylococcal nuclease, A69T + A90S and H121P, whose unfolding by denaturant is, respectively, either significantly more (28%) or significantly less (28%) cooperative than that observed for wild-type (WT). This cooperativity coefficient or m value has been shown to correlate with delta A(u). If, in turn, delta Vu is correlated with delta A(u), we would expect the m+ mutant, A69T + A90S, to exhibit a delta Vu that is more negative than WT nuclease, while the delta Vu for the m- mutant, H121P, should be smaller in absolute value. To verify the correlation between m value and delta A(u) for these mutants, we determined the xylose concentration dependence of the stability of each mutant at atmospheric pressure and as a function of pressure. The efficiency of xylose stabilization was found to be much greater for the m+ mutant than for WT, consistent with an increase in delta A(u), while that of the m- mutant was found to be only slightly greater than for WT, indicating that other factors may contribute to the denaturant m value in this case. Regardless of the denaturant m value or the effect of xylose on stability, the volume changes upon unfolding for both mutants were found to be within error of that observed for WT. Thus, there does not appear to be a correlation between the volume change and the change in exposed surface area upon unfolding. We have previously shown a lack of pH dependence of the volume change, ruling out electrostriction as a dominant contribution to delta Vu of nuclease. These studies implicate either compensation between polar and nonpolar hydration or excluded volume effects as the major determinant for the value of delta Vu.
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PMID:Testing the correlation between delta A and delta V of protein unfolding using m value mutants of staphylococcal nuclease. 875 89

The effect of xylose on the rates of folding and unfolding of staphylococcal nuclease (nuclease) have been investigated using fluorescence-detected pressure-jump relaxation kinetics in order to establish the kinetic basis for the observed stabilization of nuclease by this sugar (Frye KJ, Perman CS, Royer CA, 1996, Biochemistry 35:10234-10239). The activation volumes for both folding and unfolding and the equilibrium volume change for folding were all positive. Their values were within experimental error of those reported previously (Vidugiris GJA, Markley JL, Royer CA, 1995, Biochemistry 34:4909-4912) and were independent of xylose concentration. The major effect of xylose concentration was to increase significantly the rate of folding. The large positive activation volume for folding was interpreted previously as indicating that the rate-limiting step in nuclease folding involves dehydration of a significant amount of surface area. A large effect of xylose on the rate constant for folding provides strong support for this interpretation, because xylose, an osmolyte, stabilizes the folded state of proteins through surface tension effects. These studies further characterize the transition state in nuclease folding as lying closer to the folded, rather than the unfolded state along the folding coordinate in terms of the degree of burial of surface area. The image of the transition state that emerges is consistent with a dry molten globule.
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PMID:The kinetic basis for the stabilization of staphylococcal nuclease by xylose. 909 88

A new controlled production system to target heterologous proteins to cytoplasm or extracellular medium is described for Lactococcus lactis NCDO2118. It is based on the use of a xylose-inducible lactococcal promoter, P(xylT). The capacities of this system to produce cytoplasmic and secreted proteins were tested using the Staphylococcus aureus nuclease gene (nuc) fused or not to the lactococcal Usp45 signal peptide. Xylose-inducible nuc expression is tightly controlled and resulted in high-level and long-term protein production, and correct targeting either to the cytoplasm or to the extracellular medium. Furthermore, this expression system is versatile and can be switched on or off easily by adding either xylose or glucose, respectively. These results confirm the potential of this expression system as an alternative and useful tool for the production of proteins of interest in L. lactis.
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PMID:A xylose-inducible expression system for Lactococcus lactis. 1547 67