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)

Heat capacity, intrinsic viscosity and ellipticity of a number of globular proteins (pancreatic ribonuclease A, staphylococcal nuclease, hen egg-white lysozyme, myoglobin and cytochrome c) and a fibrillar protein (collagen) in various states (native, denatured, with and without disulfide crosslinks or a heme) have been studied experimentally over a broad range of temperatures. It is shown that the partial heat capacity of denatured protein significantly exceeds the heat capacity of native protein, especially in the case of globular proteins, and is close to the value calculated for an extended polypeptide chain from the known heat capacities of individual amino acid residues. The significant residual structure that appears at room temperature in the denatured states of some globular proteins (e.g. myoglobin and lysozyme) at neutral pH results in a slight decrease of the heat capacity, probably due to partial screening of the protein non-polar groups from water. The heat capacity of the unfolded state increases asymptotically, approaching a constant value at about 100 degrees C. The temperature dependence of the heat capacity of the native state, which can be determined over a much shorter range of temperature than that of the denatured state and, correspondingly, is less certain, appears to be linear up to 80 degrees C. Therefore, the denaturational heat capacity increment seems to be temperature-dependent and is likely to decrease to zero at about 140 degrees C.
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PMID:Heat capacity and conformation of proteins in the denatured state. 253 36

Chick embryos, chick embryo fibroblasts, and Rous sarcoma virus-transformed chick embryo fibroblasts contain a factor that preferentially blocks the accumulation of DNA-directed RNA polymerase II transcripts. The factor was detected by inhibition of transcription in a cell-free assay system utilizing partially purified RNA polymerase II from calf thymus, soluble factors from HeLa cells, and a purified DNA template. At low concentrations, it specifically prevents the accumulation of RNA polymerase II transcripts; at higher concentrations, it blocks the accumulation of other transcripts. The factor has been partially purified by sequential chromatography on BioRex 70, DNA-cellulose, Bio-Gel P-6, and HPX-87 from extracts of chicken embryos. The activity was resistant to treatment with trypsin, pronase, or micrococcal nuclease. A partial characterization of the molecule indicates that (i) it has an apparent molecular mass of about 200-300 daltons, (ii) it is stable at pH 2 and pH 12 and to heating at 100 degrees C, (iii) it is not extractable by ether or chloroform:methanol, (2:1, v/v), and (iv) it is labile to heating at 800 degrees C. These data suggest that it is a small, hydrolphilic compound probably organic in nature. The factor is active in a transcription assay utilizing either the Rous sarcoma virus Long Terminal Repeat promoter or the chick alpha 2 (Type I) collagen-promoter as DNA templates. The accumulation of promoter-specific transcripts is blocked in a cell-free assay utilizing either Rous sarcoma virus-chick embryo fibroblast extracts or HeLa S-100 factors and calf thymus RNA polymerase II. In the absence of S-100, the factor does not appreciably affect the accumulation of randomly initiated transcripts produced by calf thymus RNA polymerase II on a DNA template; this result indicates the factor interacts directly or indirectly with some component(s) of HeLa S-100 to prevent the accumulation of RNA.
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PMID:Chicken embryo extracts contain a factor that preferentially blocks the accumulation of RNA polymerase II transcripts in a cell-free system. 713 Jan 91

One of the key challenges in modeling protein energetics is the treatment of solvent interactions. This is particularly important in the case of peptides, where much of the molecule is highly exposed to solvent due to its small size. In this study, we develop an empirical method for estimating the local dielectric constant based on an additive model of atomic polarizabilities. Calculated values match reported apparent dielectric constants for a series of Staphylococcus aureus nuclease mutants. Calculated constants are used to determine screening effects on Coulombic interactions and to determine solvation contributions based on a modified Generalized Born model. These terms are incorporated into the protein modeling platform protCAD, and benchmarked on a data set of collagen mimetic peptides for which experimentally determined stabilities are available. Computing local dielectric constants using atomistic protein models and the assumption of additive atomic polarizabilities is a rapid and potentially useful method for improving electrostatics and solvation calculations that can be applied in the computational design of peptides.
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PMID:Empirical estimation of local dielectric constants: Toward atomistic design of collagen mimetic peptides. 2578 56