Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Motile extracts have been prepared from Dictyostelium discoideum by homogenization and differential centrifugation at 4 degrees C in a stabilization solution (60). These extracts gelled on warming to 25 degrees Celsius and contracted in response to micromolar Ca++ or a pH in excess of 7.0. Optimal gelation occurred in a solution containing 2.5 mM ethylene glycol-bis (beta-aminoethyl ether)N,N,N',N'-tetraacetate (EGTA), 2.5 mM piperazine-N-N'-bis [2-ethane sulfonic acid] (PIPES), 1 mM MgC1(2), 1 mM ATP, and 20 mM KCI at ph 7.0 (relaxation solution), while micromolar levels of Ca++ inhibited gelation. Conditions that solated the gel elicited contraction of extracts containing myosin. This was true regardless of whether chemical (micromolar Ca++, pH >7.0, cytochalasin B, elevated concentrations of KCI, MgC1(2), and sucrose) or physical (pressure, mechanical stress, and cold) means were used to induce solation. Myosin was definitely required for contraction. During Ca++-or pH-elicited contraction: (a) actin, myosin, and a 95,000-dalton polypeptide were concentrated in the contracted extract; (b) the gelation activity was recovered in the material sqeezed out the contracting extract;(c) electron microscopy demonstrated that the number of free, recognizable F-actin filaments increased; (d) the actomyosin MgATPase activity was stimulated by 4- to 10-fold. In the absense of myosin the Dictyostelium extract did not contract, while gelation proceeded normally. During solation of the gel in the absense of myosin: (a) electron microscopy demonstrated that the number of free, recognizable F- actin filaments increased; (b) solation-dependent contraction of the extract and the Ca++-stimulated MgATPase activity were reconstituted by adding puried Dictyostelium myosin. Actin purified from the Dictyostelium extract did not gel (at 2 mg/ml), while low concentrations of actin (0.7-2 mg/ml) that contained several contaminating components underwent rapid Ca++ regulated gelation. These results indicated : (a) gelation in Dictyostelium extracts involves a specific Ca++-sensitive interaction between actin and several other components; (b) myosin is an absolute requirement for contraction of the extract; (c) actin-myosin interactions capable of producing force for movement are prevented in the gel, while solation of the gel by either physical or chemical means results in the release of F-actin capable of interaction with myosin and subsequent contraction. The effectiveness of physical agents in producting contraction suggests that the regulation of contraction by the gel is structural in nature.
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PMID:The contractile basis of amoeboid movement. V. The control of gelation, solation, and contraction in extracts from Dictyostelium discoideum. 2 Apr 47

We have investigated three aspects of RNA turmor virus replication and cell transformation: (1) the properties of the purified avian and mammalian viral RNA-directed DNA polumerase, (2) some characteristics of the viral 60-70S RNA genome, 30-40S RNA subunits and intracellular viral RNA species, and (3) the interaction of the viral DNA polymerase with its RNA template early during infection and cell transformation by the murine sarcoma-leukemia virus (MSV[MLV]). Avian myeloblastosis virus (AMV) contains two forms of RNA-directed DNA polymerase, alpha, consisting of a single polypeptide of molecular weight 65,000, and alphabeta, consisting of two polypeptides of molecular weights 65,000 and 105,000. The alpha and alphabeta forms of AMV DNA polymerase both possess RNase H activity that requires free end termini on the ribopolymer and can degrade the RNA of the RNA-DNA hybrid in the 3' to 5' and 5' to 3' directions. But, alpha and alphabeta possess a different mode of exoribonuclease activity. While alphabeta RNase H is a processive exoribonuclease that degrades the polynucleotide chain to a core residue before attacking a second chain, alpha RNase H is a random exoribonuclease that releases the polynucleotide after each scission. Highly purified Moloney-MSV(MLV) DNA polymerase has both RNase H activity and the ability to read viral 60-70S RNA. These activities comigrate through five different steps of purification and are present at levels comparable to those found in purified AMV DNA polymerase. The MSV(MLV) 60-70S RNA genome and 35S RNA subunits were shown by periodate oxidationtritiated borohydride reduction to contain adenosine as the major 3'-terminal nucleoside. Poly (A) segments were isolated from viral 60-70S and 35S RNA by treatment with RNase A or RNase T1 and purified by afinity chromatography and gel electrophoresis. Viral poly(A) was shown to be present at the 3' terminus as -G(C,U)A190AOH. The similar sequence reported for poly(A) present in mammalian mRNA suggests that similar mechanisma are involved in the transcription and processing of both cellular and viral DNA sequences. Within transformed cells replicating MSV(MLV), viral 35S and 20S RNA were found in membrane-bound polyribosomes, whereas only 35S RNA was detected in free polyribosomes. The origin and function of 20S RNA is unknown. The early events during rapid infection and cell transformation of mouse 3T6 cells by the Harvey strain of MSV(MLV) were studied. By both autoradiographic analysis and molecular hybridization, viral DNA synthesis was detected in the cytoplasm by 1 hour after infection, reached a maximum at 2 hours, and subsequently decreased. Cytological chase experiments produced evidence that cytoplasmic viral DNA was transported to the nucleus. In situ hybridization experiments using radioactive viral DNA product as a probe demonstrated the rapid association of viral DNA sequences with the chromocenters of interphase nuclei and with the centromeric heterochromatin regions of some chromosomes.
Cold Spring Harb Symp Quant Biol 1975
PMID:Properties of oncornavirus RNA-directed DNA polymerase, the RNA template, and the intracellular products formed early during infection and cell transformation. 5 Sep 2

1. Prolonged treatment of coupling factor I (CF1) from spinach chloroplasts with trypsin free of chymotrypsin yielded an active ATPase. The isolated preparation showed only two polypeptide chains (mol wt 55,000 to 60,000) on acrylamide gels run in the presence of sodium dodecyl sulfate. The three smaller subunits of CF1 were not detectable. The preparation no longer served as a coupling factor for photophosphorylation in either EDTA- or silicotungstate-treated chloroplasts. 2. An antiserum prepared against coupling factor I from chloroplasts inhibited the ATPase activity of the trypsin-treated CF1. In contrast, antisera prepared against the two individual (denatured) subunits did not inhibit the ATPase activity when tested either alone or together, although each interacted with the trypsin-treated protein, forming precipitin lines in Ouchterlony plates. 3. The trypsin-treated enzyme was still cold-labile, showing that the three smaller subunits are not required for this property. However, the enzyme was no longer sensitive to the natural inhibitor protein which is one of its subunits (subunit epislon), but was still sensitive to inhibition by the flavonoid quercetin. 4. Two equivalents of 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole were sufficient to inhibit about 80% of the ATPase activity of the coupling factor, irrespective of whether it contained two of five subunits. The inhibition was completely reversed by dithiothreitol. 5. Triated 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole was prepared. Treatment of the coupling factor with this tritium-labeled inhibitor followed by electrophoresis on acrylamide gels revealed that most of the radioactivity was incorporated into the beta subunit of the enzyme (molecular weight 56,000).
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PMID:Partial resolution of the enzymes catalyzing photophosphorylation. XV. Approaches to the active site of coupling factor I. 12 75

Actin, myosin, and a high molecular weight actin-binding protein were purified from chronic myelogenous leukemia (CML) leukocytes. CML leukocyte actin resembled skeletal muscle and other cytoplasmic actins by its subunit molecular weight, by its ability to polymerize in the presence of salts, and to activate the Mg2+-ATPase activity of rabbit skeletal muscle myosin. CML leukocyte myosin was similar to other vertebrate cytoplasmic myosins in having heavy chains and two light subunits. However, its apparent heavy-chain molecular weight and Stokes radius suggested that it was variably degraded during purification. Purified CML leukocyte myosin had average specific EDTA- AND Ca2+-activated ATPase activities of 125 and 151 nmol Pi released/mg protein per min, respectively and low specific Mg2+-ATPase activity. The Mg2+-ATPase activity of CML myosin was increased 200-fold by rabbit skeletal muscle F-actin, but the specific activity relative to that of actin-activated rabbit skeletal muscle myosin was low. CML leukocyte myosin, like other vertebrate cytoplasmic myosins, formed filaments in 0.1 M KCl solutions. Reduced and denatured CML leukocyte-actin-binding protein had a single high molecular weight subunit like a recently described actin-binding protein of rabbit pulmonary macrophages which promotes the polymerization and gelation of actin. Cytoplasmic extracts of CML leukocytes prepared with ice-cold 0.34-M sucrose solutions containing Mg2+-ATP, dithiothreitol, and EDTA at pH 7.0 underwent rapid gelation when warmed to 25 degrees C. Initially, the gel could be liquified by cooling to ice-bath temperature. With time, warmed cytoplasmic extract gels shrunk ("contracted") into aggregates. The following findings indicated that CML leukocyte actin-binding protein promoted the temperature-dependent gelation of actin in the cytoplasmic extracts and that CML leukocyte myosin was involved in the contraction of the actin gels: (a) Cytoplasmic extract gels initially contained actin as their major polypeptide component and consistent of tangled thin filaments; (b) Contracted aggregates of cytoplasmic extract gels contained by large quantities of myosin as well as actin; (c) Purified actin-binding protein underwent a temperature-dependent, reversible aggregation and caused low concentrations of purified muscle or CML leukocyte actins to gel in sucrose solutions; (d) The gels formed from purified actin plus purified actin-binding protein slowly contracted in the presence but not in the absence of purified CML leukocyte myosin; (e) Rabbit antiserum against purified CML leukocyte actin-binding protein but not against purified CML leukocyte myosin inhibited the gelation of warmed CML leukocyte extracts. Antiserum against CML leukocyte myosin had no effect on the gelation of CML leukocyte extracts but partially curtailed the contraction of the CML leukocyte extract gels and of gels formed from purified CML leukocyte actin-binding protein plus rabbit skeletal muscle actin.
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PMID:Interactions of actin, myosin, and an actin-binding protein of chronic myelogenous leukemia leukocytes. 13 21

The expression of HSV-specific gene functions by 22 ts mutants of HSV-1 in 15 complementation groups and 8 ts mutants of HSV-2 in 7 complementation groups has been studied at the nonpermissive temperature. Four cistrons of HSV-1 and three cistrons of HSV-2 with defects in viral DNA and DAN polymerase synthesis were identified. DNA-mutants of HSV-1 revealed a greater alteration in HSV polypeptide synthesis and viral assembly than DNA- mutants of HSV-2. Mutants with apparent defects in structural proteins have been identified for both HSV-1 and HSV-2 as demonstrated by their increased themolability. The general organization of the provisional HSV-1 and HSV-2 linkage maps revealed a similarity in the arrangement of functionally related cistrons, with DNA- mutants being located on the left-hand side of each map and mutants with phenotypic properties similar to those of the wild-type virus, on the right-hand side. An early polypeptide of HSV (VP175, MW 175,000) was found to accumulate in cells infected at the nonpermissive temperature withts mutants of HSV-1 in complementation group B. The VP175 polypeptide was isolated from such cells by a combination of SDS-preparative and analytical disc gel electrophoresis. Antiserum prepared to this polypeptide was found to descriminate between HSV-1 and HSV-2 by immunofluorescence. On the other hand, type-specific gene functions of HSV-1 and HSV-2 were not demonstrated through intertypic complementation and recombination tests with heterologous mutant pairs, whereas mutually exchangeable or common gene functions were readily identified. Eight ts mutants of HSV-2 were used to detect functional HSV genes in hamster embryo cells transformed by HSV-2. Normal hamster cells and SV40-transformed hamster cells failed to support the replication of the mutants at the nonpermissive temperature. However, the replication of two mutants, defective in late functions, was significantly enhanced in two independently derived HSV-2-transformed cell lines. Thus functional HSV genetic information was detected in HSV-2-transformed cells through the use of ts mutants. Moreover, it appears that the information present in both cell lines is not only specific but involves late HSV functions.
Cold Spring Harb Symp Quant Biol 1975
PMID:Viral gene functions expressed and detected by temperature-sensitive mutants of herpes simplex virus. 16 28

The high-density lipoproteins (HDL) of human serum appear to be unstable and easily exposed to chemical changes during isolation. In earlier studies we have isolated and purified HDL subfractions either in the presence of an SH-blocking agent, DTNB, or in the cold. By both procedures reproducible lipoprotein subfractions could be recovered by hydroxyl apatite column chromatography at the elution steps 0.03-0.05 mol/l (subfraction II) and 0.05-0.15 mol/l phosphate buffer (subfraction III). The protein moiety of both lipoprotein subfractions contained polypeptides A-I , A-II, thin line (TL), C-I and C-II, and the protein moiety of subfraction III contained also C-III. The incubation at 37 degrees C of these HDL subfractions gave reproducible daughter lipoprotein fractions that could be recovered by subsequent rechromatography on hydroxyl apatite. At each of the elution steps 0.05-0.075 mol/l and 0.075-0. mol/l one daughter fraction was recovered, the protein moiety of which was composed of polypeptide A-I, as judged by polyacrylamide gel electrophoresis, immunodiffusion, and amino acid analysis. The incubation of parent subfractions II and III caused also the appearance at elution step 0.001-0.01 mol/l of a daughter lipoprotein fraction - lipoprotein A (Lp-A) - that was characterized by a protein moiety with polypeptides A-I and A-II in equal amounts. The 'release' of lipoprotein A-I (Lp-A-I) and Lp-A was shown to be due rather to the incubation than to the column chromatography as such. The chemical changes occurring during the incubation of HDL suggested a degradation of phosphatidylcholine (PC) to lysophosphatidylcholine (lyso-PC) and glycerylphosphorylcholine (GPC). It is suggested that the degradation of PC might interfere with the interaction between the lipoprotein families composing HDL.
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PMID:Studies on human serum high-density lipoproteins (HDL). IV. Isolation of lipoprotein families after incubation of HDL. 17 62

Purified high-density lipoprotein (HDL), obtained by preparative ultracentrifugation at density 1.063-1.19 g/ml in the cold, were subfractionated by hydroxyl apatite column chromatography. Two of the obtained subfractions (subfractions II and III) turned turbid after incubation at 37 degrees C for 12 h. The turbid material was recovered in the supernatant of D 1.006 g/ml after centriguation at 30,000 g for 2 h. The lipoprotein fraction causing the turbidity was composed of 94% cholesterol ester and 2% apolipoprotein (by weight). On polyacrylamide gel electrophoresis the apolipoprotein moiety appeared as one polypeptide with the electrophoretic mobility of polypeptide A-I, revealed a blocked NH2-terminal amino acid, and had a total amino acid composition that differed from that of A-I and of the arginine-rich polypeptide.
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PMID:Studies on human serum high-density lipoproteins. V. Isolation and characterization of a cholesterol ester-rich lipoprotein after in vitro incubation. 17 17

Rat liver parenchymal cell binding, uptake, and proteolytic degradation of rat 125I-labeled high density lipoprotein (HDL) subfraction, HDL3 (1.10 less than d less than 1.210 g/ml), in which apo-A-I is the major polypeptide, were investigated. Structural and metabolic integrity of the isolated cells was verified by trypan blue exclusion, low lactic dehydrogenase leakage, expected morphology, and gluconeogenesis from lactate and pyruvate. 125I-labeled HDL3 was incubated with 10 X 10(6) cells at 37 degrees and 4 degrees in albumin and Krebs-Henseleit bicarbonate buffer, pH 7.4. Binding and uptake were determined by radioactivity in washed cells. Proteolytic degradation was determined by trichloroacetic acid-soluble radioactivity in the incubation medium. At 37 degrees, maximum HDL3 binding (Bmax) and uptake occurred at 30 min with a Bmax of 31 ng/mg dry weight of cells. The apparent dissociation constant of the HDL3 receptor system (Kd) was 60 X 10(-8) M, based on Mr = 28,000 of apo-A-I, the predominant rat HDL3 protein. Proteolytic degradation showed a 15-min lag and then constant proteolysis. After 2 hours 5.8% of incubated 125I-labeled HDL3 was degraded. Sixty per cent of cell radioactivity at 37 degrees was trypsin-releasable. At 37 degrees, 125I-labeled HDL3 was incubated with cells in the presence of varying concentrations of native (cold) HDL3, very low density lipoproteins, and low density lipoproteins. Incubation with native HDL3 resulted in greatest inhibition of 125I-labeled HDL3 binding, uptake, and proteolytic degradation. When 125I-labeled HDL3 was preincubated with increasing amounts of HDL3 antiserum, binding and uptake by cells were decreased to complete inhibition. Cell binding, uptake, and proteolytic degradation of 125I-labeled HDL3 were markedly diminished at 4 degrees. Less than 1 mM chloroquine enhanced 125I-labeled HDL3 proteolysis but at 5 mM or greater, chloroquine inhibited proteolysis with 125I-labeled HDL3 accumulation in cells. L-[U-14C]Lysine-labeled HDL3 was bound, taken up, and degraded by cells as effectively as 125I-labeled HDL3. These data suggest that liver cell binding, uptake, and proteolytic degradation of rat HDL3 are actively performed and linked in the sequence:binding, then uptake, and finally proteolytic degradation. Furthermore, there may be a specific HDL3 (lipoprotein A) receptor of recognition site(s) on the plasma membrane. Finally, our data further support our previous reports of the important role of liver lysosomes in proteolytic degradation of HDL3.
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PMID:Rat high density lipoprotein subfraction (HDL3) uptake and catabolism by isolated rat liver parenchymal cells. 18 84

(1) The effects of cold adaptation upon the brown adipose tissue have been studied in rats, hamsters, mice, and guinea pigs. (2) Striking effects were found for total tissue as well as at the mitochondrial level, e.g., increases in protein and phospholipid contents, changes in phospholipid fatty acid composition (a decrease in the percentage of palmitic and palmitoleic acids and an increase in stearic and linoleic acids), and a change in the mitochondrial polypeptide composition (a marked increase in a 32000 molecular weight polypeptide, except for hamsters). (3) In situations where animals exhibit a greatly enhanced capacity for nonshivering thermogenesis (cold adaptation for rats, mice, and guinea pigs, birth for guinea pigs, and hibernation ability for hamsters, dormice, and garden dormice), brown fat mitochondria are characterized by the occurrence of large amounts of the 32000 molecular weight polypeptide characteristic of these mitochondria.
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PMID:Changes induced by cold adaptation in the brown adipose tissue from several species of rodents, with special reference to the mitochondrial components. 23 94

Torpedo californica postsynaptic membrane fragments were treated with base, which resulted in membranes that were depleted of many nonacetylcholine receptor polypeptides and contained acetylcholine receptor subunits of Mr 40,000, 50,000, 60,000, and 65,000 (Raftery, M.A., Vandlen, R.L., Reed, K.L. & Lee T. (1975) Cold Spring Harbor Symp. Quant. Biol. 40, 193-202). A 43,000-Mr polypeptide and some other components were quantitatively extracted. Base-treated membranes retained the capacity to bind [3H]perhydrohistrionicotoxin and the local anesthetics dibucaine and tetracaine. The regulation of this binding by carbamylcholine, as well as the kinetic mechanism of perhydrohistrionicotoxin binding, was unchanged. [3H]Perhydrohistrionicotoxin binding activity was largely reconstituted from 2% sodium cholate extracts of base-treated membranes. Therefore, the perhydrostrionicotoxin binding site appears to be located on one or more of the acetylcholine receptor polypeptides, and the reconstitution of that binding site from detergent extracts does not require the presence of a 43,000-Mr polypeptide.
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PMID:Specific binding of perhydrohistrionicotoxin to Torpedo acetylcholine receptor. 28 47


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