Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The hydrophobicity of the subdomain 3/4 hydrophobic loop (262-274) has been implicated to be essential for actin's function. We previously showed (Kuang, B., and Rubenstein, P. A. (1997) J. Biol. Chem. 272, 1237-1247) that a mutant yeast actin (V266G/L267G) with markedly decreased hydrophobicity in this loop conferred severe cold sensitivity to its polymerization. Here we further tested the mutational effect on the conformation and function of G-actin. This GG mutation caused no significant changes in overall secondary structure or in the microenvironment around actin's tryptophan residues, nor did it alter the dissociation constant of G-actin for ATP. However, it lowers the intrinsic ATPase activity and the melting temperature for Mg-GG actin from 51 to 33 degrees C and transforms the conformation of subdomain 2 and the central cleft of G-actin into an F-monomer-like structure. The results suggest that the hydrophobic plug may not only play a role in actin filament stabilization but also may be important for controlling the stability of G-actin and for promoting the conformational change of the monomer needed for addition to a growing actin filament.
 ...
PMID:The effects of severely decreased hydrophobicity in a subdomain 3/4 loop on the dynamics and stability of yeast G-actin. 902 Jan 64

Three cold-sensitive mutants in phage P22 coat protein have been characterized to determine the effects of the amino acid substitutions that cause cold sensitivity on the folding pathway and the conformation of refolded coat protein. Here we find that the three cold-sensitive mutants which have the threonine residue at position 10 changed to isoleucine (T10I), the arginine residue at position 101 changed to cysteine (R101C), or the asparagine residue at position 414 changed to serine (N414S) were capable of folding from a denatured state into a soluble monomeric species, but in each case, the folded conformation was altered. Changes in the kinetics of folding were observed by both tryptophan and bisANS fluorescence. In contrast to the temperature-sensitive for folding coat protein mutants which can be rescued at nonpermissive temperatures in vivo by the overproduction of molecular chaperones GroEL and GroES [Gordon, C. L., Sather, S. K., Casjens, S., & King, J. (1994) J. Biol. Chem. 269, 27941-27951], the folding defects associated with the cold-sensitive amino acid substitutions were not recognized by GroEL and GroES.
 ...
PMID:The folded conformation of phage P22 coat protein is affected by amino acid substitutions that lead to a cold-sensitive phenotype. 909 27

The folding and stability of maltose binding protein (MBP) have been investigated as a function of pH and temperature by intrinsic tryptophan fluorescence, far- and near-UV circular dichroism, and high-sensitivity differential scanning calorimetric measurements. MBP is a monomeric, two-domain protein containing 370 amino acids. The protein is stable in the pH range of 4-10.5 at 25 degrees C. The protein exhibits reversible, two-state, thermal and guanidine hydrochloride-mediated denaturation at neutral pH. The thermostability of MBP is maximal at pH 6, with a Tm of 64.9 degrees C and a deltaHm of 259.7 kcal mol(-1). The linear dependence of deltaHm on Tm was used to estimate a value of deltaCp of 7.9 kcal mol(-1) K(-1) or 21.3 cal (mol of residue)(-1) K(-1). These values are higher than the corresponding deltaCp's for most globular proteins studied to date. However, the extrapolated values of deltaH and deltaS (per mole of residue) at 110 degrees C are similar to those of other globular proteins. These data have been used to show that the temperature at which a protein undergoes cold denaturation depends primarily on the deltaCp (per mol of residue) and that this temperature increases with an increase in deltaCp. The predicted decrease in stability of MBP at low temperatures was experimentally confirmed by carrying out denaturant-mediated unfolding studies at neutral pH at 2 and 28 degrees C.
 ...
PMID:Thermodynamic characterization of the reversible, two-state unfolding of maltose binding protein, a large two-domain protein. 912 24

We studied the functional effects of single amino acid substitutions in the postulated M4 transmembrane domains of Torpedo californica nicotinic acetylcholine receptors (nAChRs) expressed in Xenopus oocytes at the single-channel level. At low ACh concentrations and cold temperatures, the replacement of wild-type alpha418Cys residues with the large, hydrophobic amino acids tryptophan or phenylalanine increased mean open times 26-fold and 3-fold, respectively. The mutation of a homologous cysteine in the beta subunit (beta447Trp) had similar but smaller effects on mean open time. Coexpression of alpha418Trp and beta447Trp had the largest effect on channel open time, increasing mean open time 58-fold. No changes in conductance or ion selectivity were detected for any of the single subunit amino acid substitutions tested. However, the coexpression of the alpha418Trp and beta447Trp mutated subunits also produced channels with at least two additional conductance levels. Block by acetylcholine was apparent in the current records from alpha418Trp mutants. Burst analysis of the alpha418Trp mutations showed an increase in the channel open probability, due to a decrease in the apparent channel closing rate and a probable increase in the effective opening rate. Our results show that modifications in the primary structure of the alpha- and beta subunit M4 domain, which are postulated to be at the lipid-protein interface, can significantly alter channel gating, and that mutations in multiple subunits act additively to increase channel open time.
 ...
PMID:Mutations in the M4 domain of the Torpedo californica nicotinic acetylcholine receptor alter channel opening and closing. 921 18

We have previously shown that the injury to cultured liver endothelial cells during cold incubation in University of Wisconsin (UW) solution is energy-dependent and is mediated by reactive oxygen species. Here we demonstrate that this reactive oxygen-mediated injury is specific neither to endothelial cells nor to UW solution: cultured hepatocytes incubated in cold (4 degrees C) UW solution or histidine-tryptophan-ketoglutarate (HTK) solution were injured under normoxic conditions (loss of viability, 63% +/- 10% after 48 hours of cold incubation in UW solution and 82% +/- 11% after 24 hours of cold incubation in HTK solution), whereas hypoxia was protective (loss of viability, 29% +/- 12% [UW] and 13% +/- 3% [HTK] after the same cold incubation times). The injury under normoxic conditions was also largely decreased by adding either the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) or the flavonoid silibinin to the solutions, or by preincubating the cells with the iron chelator deferoxamine before the hypothermic incubation. Marked lipid peroxidation was observed during cold incubation in both preservation solutions. These results suggest that the injury to cultured hepatocytes during cold incubation in UW and HTK solutions is mediated by reactive oxygen species as is the injury to cultured liver endothelial cells.
 ...
PMID:Oxygen-free radical-mediated injury to cultured rat hepatocytes during cold incubation in preservation solutions. 925 45

Warm ischemia is known to induce substantial damage to the liver parenchyma. With respect to clinical liver transplantation, the tolerance of the liver to warm ischemia and the preservation of these organs have not been studied in detail. In isolated reperfused pig livers we proceeded according to the following concept: Livers were subjected to 1 or 3 h of warm ischemia. Subsequently, these organs were preserved by either normothermic perfusion or cold storage (histidine-tryptophan-alpha-ketoglutarate, HTK) for 3 h each. After storage, liver function was assessed in a reperfusion circuit for another 3 h. Parameters under evaluation were bile flow, perfusion flow, oxygen consumption, enzyme release into the perfusate (creatine kinase, glutamic oxaloacetic transaminase (GOT), lactic dehydrogenase, and glutamic pyruvic transaminase), and histomorphology. Damage to the liver was lowest after warm ischemia of 1 h. The results after cold storage were superior to those after normothermic perfusion (GOT: 3.2 +/- 0.3 and 2.6 +/- 0.2 U/g liver; cumulative bile production: 14.7 +/- 2.1 and 9.4 +/- 1 ml, respectively; P < 0.05). In contrast, we found substantial damage at the end of reperfusion in livers undergoing 3 h of warm ischemia under both preservation techniques with severe hepatocellular pyknoses and essentially altered nonparenchymal cells. The results suggest that pig livers undergoing 1 h of warm ischemia and cold storage for 3 h with HTK solution may lead to functioning after transplantation.
 ...
PMID:Preservation of pig liver allografts after warm ischemia: normothermic perfusion versus cold storage. 939 99

We have shown earlier that restraint-cold stress-induced gastric ulceration in rats is caused by metal ion-dependent generation of hydroxyl radical (OH.) and oxidative inactivation of the gastric peroxidase (GPO), an important H2O2 scavenging enzyme. To study the mechanism of the oxidative damage of GPO, the purified enzyme was exposed to an OH. generating system containing Cu2+, ascorbate, and H2O2. Kinetic studies indicate that the enzyme is inactivated in a time-dependent process showing saturation with respect to Cu2+ concentration. The enzyme specifically requires Cu2+ and is not inactivated by the same concentration of Fe2+, Mn2+, or Zn2+. Sensitivity to catalase indicates the critical role of H2O2 in the inactivation. Inactivation is insensitive to superoxide dismutase, suggesting no role of superoxide. The rate of inactivation is not increased in D2O excluding the involvement of singlet oxygen in the process. However, OH. scavengers such as benzoate or mannitol cannot prevent inactivation. The results indicate a plausible generation of OH. within the enzyme molecule as the cause of inactivation. Fragmentation of peptide linkage or intramolecular crosslinking, gross change of tertiary structure, or change in intrinsic tryptophan fluorescence which occurs in "global" oxidation are not evident. Inactivation is dependent on pH and from a plot of K(obs) of inactivation against pH, the controlling role of an ionizable group of the enzyme having a pka of 7.8 could be suggested, deprotonation of which favors inactivation. Amino acid analysis shows a specific loss of two lysine residues in the inactivated enzyme. Competitive kinetic studies indicate that pyridoxal phosphate, a specific modifier of the lysine residue, prevents inactivation by competing with Cu2+ for binding at the GPO. A Cu2+ binding motif consisting at least of two lysine residues exists in GPO, which specifically binds Cu2+ and generates OH.. The radical oxidizes the lysine residues and perturbs the heme environment to cause inactivation. We suggest that oxidative damage of GPO is mediated by site-specific generation of OH. and not by the OH. generated in the bulk phase.
 ...
PMID:Oxidative inactivation of gastric peroxidase by site-specific generation of hydroxyl radical and its role in stress-induced gastric ulceration. 943 59

chkYB-2 is a sequence-specific, single-stranded DNA binding chicken Y-box protein that promotes Rous sarcoma virus long terminal repeat (RSV LTR)-driven transcription in avian fibroblasts. The DNA-binding domain of chkYB-2 has been mapped by characterizing the DNA binding properties of purified recombinant chkYB-2 mutant polypeptides. The data indicate that the invariant cold shock domain (CSD) is necessary but not sufficient for association with DNA and suggest that another conserved region, adjacent to the carboxyl boundary of the CSD, plays a role in high-affinity DNA binding. chkYB-2 binds to a tandem repeat of the 5'-GTACCACC-3' motif on the RSV LTR. Mutational analysis of this recognition sequence revealed the requirement of an essentially unaltered template for both high-affinity binding by chkYB-2 as well as maximal transcriptional activity of the RSV LTR in vivo. The single-stranded DNA binding activity of chkYB-2 is augmented by Mg2+. The possible significance of this finding for transactivation by a single-strand DNA binding protein is discussed.
 ...
PMID:Characterization of the DNA-binding domain of the avian Y-box protein, chkYB-2, and mutational analysis of its single-strand binding motif in the Rous sarcoma virus enhancer. 944 81

The temperature dependence of the pressure-induced equilibrium unfolding of staphylococcal nuclease (Snase) was determined by fluorescence of the single tryptophan residue, FTIR absorption for the amide I' and tyrosine O-H bands, and small-angle X-ray scattering (SAXS). The results from these three techniques were similar, although the stability as measured by fluorescence was slightly lower than that measured by FTIR and SAXS. The resulting phase diagram exhibits the well-known curvature for heat and cold denaturation of proteins, due to the large decrease in heat capacity upon folding. The volume change for unfolding became less negative with increasing temperatures, consistent with a larger thermal expansivity for the unfolded state than for the folded state. Fluorescence-detected pressure-jump kinetics measurements revealed that the curvature in the phase diagram is due primarily to the rate constant for folding, indicating a loss in heat capacity for the transition state relative to the unfolded state. The similar temperature dependence of the equilibrium and activation volume changes for folding indicates that the thermal expansivities of the folded and transition states are similar. This, along with the fact that the activation volume for folding is positive over the temperature range examined, the nonlinear dependence of the folding rate constant upon temperature implicates significant dehydration in the rate-limiting step for folding of Snase.
 ...
PMID:Exploring the temperature-pressure phase diagram of staphylococcal nuclease. 1019 32

The quality of organ preservation is of major importance in minimizing the incidence of primary graft nonfunction and organ rejection. For this study a new semiquantitative score was developed that grades morphologic tissue alterations in the liver according to their frequency and severity. It was applied to assess commonly used perfusion solutions for their efficacy in preventing early and late tissue damage after rat liver transplantation. For transplantation the livers were stored in Euro-Collins (EC, group I; n = 11), histidine-tryptophan-alpha-ketoglutarate (HTK, group II; n = 11), or University of Wisconsin solution (UW, group III; n = 11). Rat liver transplantation was performed with graft arterialization by the method of Engemann. Biopsies were taken for morphological examination and semiquantitative scoring during the donor operation, after 4 h of cold storage, 1 h after reperfusion, and 4 weeks postoperatively. An immunohistological bromodeoxyuridine (BrdU) assay was also performed on the day of dissection to assess the rate of hepatic proliferation. Semiquantitative morphological analysis gave widely differing results in all experimental groups after 4 h of ischemia. There was less intracellular and interstitial edema, fatty degeneration, intralobular necrosis, and hepatocellular proliferation in the HTK group than in the other groups. Neither after cold ischemia nor 1 h after reperfusion did Kupffer-cell activation occur; this is known to play a major role in the development ofischemia and reperfusion injury. Furthermore, late changes such as bile-duct proliferation and vascular and sinusoidal alterations appeared less frequently in this group. The hepato-protective powers of HTK solution might therefore be due to decreased Kupffer-cell activation.
 ...
PMID:Organ preservation with EC, HTK, and UW, solution in orthotopic rat liver transplantation. Part II. Morphological study. 1050 Oct 78


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>