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Query: UNIPROT:P50583 (asymmetrical)
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Three electrophoretic variants of superoxide dismutase can be detected in bovine erythrocytes by gel electrophoresis and electrofocusing. The two major forms, having isoelectric points at pH 5.2 and 4.9, were isolated by preparative focusing or chromatography. No differences were found in molecular weight, metal content, antigenicity, electron spin resonance spectrum, visible and ultraviolet optical spectra. In contrast, holo- and apo-superoxide dismutase, which have an electrophoretic mobility similar to that of the two major forms, showed unresolved isoelectric points but significantly different antigenicity. This result suggests that their different electrophoretic mobility is mainly conformation-related. The variant with pI 5.2, corresponding to the protein purified by ordinary procedures, was found to be inactivated by heat treatment faster than the other form. The latter one, on the other hand, gave rise to a multiple pattern of electrophoretic bands after incubation at 75 degrees C. It is suggested that superoxide dismutase multiplicity in erythrocytes is not genetically determined, but may be related to segregation of subunits, made non-identically by post translational asymmetrical modification.
Mol Cell Biochem 1982 Aug 20
PMID:Isolation and preliminary characterization of electrophoretic variants of copper, zinc superoxide dismutase. 713 64

The crystal structure of the self-complementary DNA octamer d(GAAGCTTC)2 complexed with N8-actinomycin D (N8AMD) has been determined at 3.0 A resolution (space group: P3(1)21; unit cell: a = 62.30, b = 62.30, c = 42.97 A; R = 0.173 for 1845 reflections). The DNA structure was severely distorted by the N8AMD bound intercalatively into the middle dinucleotide, 5'-GC-3'. The two cyclic depsipeptides, which differ from each other in overall conformation, lie in the minor groove. The complex is further stabilized by forming base--peptide and chromophore--backbone hydrogen bonds. The complexes are stacked together to form a pseudocontinuous helix running through the crystals. The structure of d(GAAGCTTC)2-actinomycin D (AMD) crystallized in the space group C2 [Kamitori S., & Takusagawa, F. (1992) J. Mol. Biol. 225, 445-456] was re-refined in order to compare it directly to the N8AMD complex structure. The asymmetrical binding mode of AMD has been confirmed on the basis of the two complex structures. The crystal structures of the N8AMD and AMD complexes bound to the same d(GAAGCTTC)2 differed by a root-mean-square deviation on all atom positions of 1.77 A, but most of the structural differences can be attributed to molecular packing in two different crystal forms, and not to structural differences induced by the interaction with the intercalating agents. However, the DNA binding and biological characteristics of N8AMD and AMD are quite different from each other. The DNA association constant of N8AMD is 33-fold less than that of AMD in an aqueous solution. N8AMD required a concentration > 10.0 microM to inhibit RNA synthesis activity in HeLa cells by 50%, whereas AMD reached to the same inhibitory level at only 35 nM. The structure of the DNA-N8AMD complex suggested that substitution of the N-methyl-L-valine residue in the cyclic depsipeptide with a N-methyl-D-valine residue might increase the hydrophobic interaction with the minor groove of the DNA. Thus the DNA association constant and RNA synthesis inhibitory activities of 5,5'-N-methyl-D-valine AMD (D-MeVal-AMD) have also been determined. The DNA association constant of D-MeVal-AMD is more than 2-fold greater than that of AMD, and the RNA synthesis inhibitory activity is about 20-fold greater.
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PMID:Structural, physical, and biological characteristics of RNA.DNA binding agent N8-actinomycin D. 754 Dec 44

We characterized a nuclear gene and its corresponding cDNA encoding beta-tubulin (gene TubB1) of the marine red alga Chondrus crispus. The deduced TubB1 protein is the most divergent beta-tubulin so far reported with only 64 to 69% amino acid identity relative to other beta-tubulins from higher and lower eukaryotes. Our analysis reveals that TubB1 has an accelerated evolutionary rate probably due to a release of functional constraints in connexion with a specialization of microtubular structures in rhodophytes. It further indicates that isoform diversity and functional differentiation of tubulins in eukaryotic cells may be controlled by independent selective constraints. TubB1 has a short spliceosomal intron at its 5' end which seems to be a characteristic feature of nuclear protein-coding genes from rhodophytes. The splice junctions of the four known rhodophyte introns comply well with the corresponding consensus sequences of higher plants in agreement with previous suggestions from phylogenetic inference that red algae and green plants may be sister groups. The paucity and asymmetrical location of introns in rhodophyte genes can be explained by differential intron loss due to conversion of genes by homologous recombination with cDNAs corresponding to reverse transcribed mRNAs or partially spliced pre-mRNAs, respectively. The identification of an intron containing TubB1 cDNA in C. crispus confirms that pre-mRNAs can escape both splicing and degradation in the nucleus prior to transport into the cytoplasm. Differential Southern hybridizations under non-stringent conditions with homologous and heterologous probes suggest that C. crispus contains a second degenerate beta-tubulin gene (or pseudogene?) which, however, is only distantly related to TubB1 as it is to the more conserved homologues of other organisms.
Plant Mol Biol 1995 May
PMID:The marine red alga Chondrus crispus has a highly divergent beta-tubulin gene with a characteristic 5' intron: functional and evolutionary implications. 759 16

The subcellular processes that correlate with early learning and memory formation in the chick and sensitive periods for this learning are discussed. Imprinting and passive avoidance learning are followed by a number of cellular processes, each of which persists for a characteristic time in certain brain regions, and may culminate in synaptic structure modification. In the chick brain, the NMDA subtype of glutamate receptor appears to play an important role in both memory formation and sensitive periods during development, similar to its demonstrated role in neural plasticity in the mammalian brain. Two important findings have emerged from the studies using chickens. First, memory formation appears to occur at multiple sites in the forebrain and, most importantly, it appears to "flow" from one site to another, leaving neurochemical traces in each as it moves on. Second, the memory is laid down either in different sites or in different subcellular events in the left and right forebrain hemispheres. Hence, we are alerted to the possibility of similar asymmetrical processes occurring in memory consolidation in the mammalian brain. The similarities between early memory formation and experience-dependent plasticity of the brain during development are discussed.
Mol Neurobiol
PMID:The molecular neurobiology of early learning, development, and sensitive periods, with emphasis on the avian brain. 791 26

Casein kinase 2 (CK-2) subunits were sublocalized by indirect immunofluorescence in synchronized primary human fibroblasts, human HT1080, and mouse 3T3 cells. The antibodies used were directed against the CK-2 alpha- and beta-subunits. In human primary fibroblasts and the fibrosarcoma (HT1080) both the alpha and beta-subunits were predominantly localized in the nucleus, irrespective of the stage of the cell cycle. By contrast, in murine 3T3 cells, CK-2 alpha-subunit was found in the cytoplasm whereas the beta-subunit was mostly localized in the nucleus. In parallel, CK-2 activity was measured throughout the cell cycle. Apart from the well-known differences between cell lines with their high proliferation rate and higher CK-2 activity, and the slower growing primary cell cultures with lower CK-2 activity, no significant activity changes were measured. Densitometric analysis of CK-2 alpha- vs. beta-subunits after immunoblot detection revealed a 10:1 ratio for primary human skin fibroblasts at quiescent state which is significantly more than at later stages. Such an asymmetrical subunit distribution at G0 was not observed with the established cell line 3T3 where the alpha/beta ratio was 0.7-1 throughout the cell cycle.
Cell Mol Biol Res 1993
PMID:Subcellular localization of protein kinase CK-2 alpha- and beta-subunits in synchronized cells from primary human fibroblasts and established cell lines. 795 15

Cystathionamine and selenocystathionamine, diamines analogous to 1,6-diaminohexane but having the third methylene group of the carbon chain substituted by a S or a Se atom, are asymmetrical thio- (seleno-) ethers. They can give rise by oxidative monodeamination to two different aminoaldehydes. It has been shown that lentil seedlings amineoxidase catalyzes the oxidative deamination of either the one or the other aminogroup of cystathionamine or of selenocystathionamine, giving rise to both possible aminoaldehydes.
Biochem Mol Biol Int 1994 Mar
PMID:On the oxidation of cystathionamine and selenocystathionamine by plant amineoxidase. 803 25

The DNA methyltransferases of type I restriction-modification systems are trimeric enzymes composed of one DNA specificity (S) subunit and two modification (M) subunits. The S subunit contains two large regions, each of which recognizes one part of the split, asymmetrical DNA target sequence. Each M subunit contains an amino acid motif for binding the methyl group donor and cofactor, S-adenosyl methionine. The EcoKI methyltransferase has a strong preference for methylating a hemimethylated DNA target rather than an unmodified target. We have used partial proteolytic digestion of EcoKI methyltransferase to generate polypeptide domains that we have identified by amino acid sequencing. The S subunit was cut into two large, folded domains each containing one DNA binding region. Binding of DNA partially protected the S subunit from digestion. The M subunit was also cut into two large domains joined together by a short flexible loop, and a C-terminal tail region. The short loop contained part of the S-adenosyl methionine binding motif, and cofactor binding protected the loop and the two large domains from proteolysis. The C-terminal domain of M remained associated with the N-terminal domain of the S subunit even after the rest of the protein had been digested. The conformation of the tail region of the M subunit was sensitive to the methylation state of DNA in ternary complexes also containing S-adenosyl methionine, and could differentiate between unmethylated and hemimethylated DNA substrates.
J Mol Biol 1994 Mar 04
PMID:The domains of a type I DNA methyltransferase. Interactions and role in recognition of DNA methylation. 812 Aug 83

Small-angle X-ray scattering of both S100b and a mixture of S100a and S100ao (S100a,ao) was measured over a protein concentration range of 1.5 to 10.0 mg/ml. The addition of trifluoroperazine (TFP) to S100 solutions suppressed higher aggregation under the conditions studied. In the presence of TFP (1 mol TFP/mol of protein dimer), the radius of gyration of S100b and S100a,ao is found to be 19.5 +/- 0.3A and 20.2 +/- 0.3A, respectively, indicating that most S100 proteins may exist as dimers under the conditions studied. The observed difference (0.7 +/- 0.3A) in the radius of gyration between S100b and S100a,ao indicates that these dimers have different, asymmetrical shapes.
Biochem Mol Biol Int 1993 Jul
PMID:Small angle X-ray scattering study of S100 proteins. 840 Dec 99

Two dimensional (2D) crystals of photosystem II (PSII) were obtained from n-heptyl-beta-D-thioglucoside-solubilized monomers of spinach PSII complex by conventional detergent dialysis. The 2D crystals were either large cylindrical vesicles (1 to 2 micrometer by 4 to 6 micrometer as flattened vesicles) or large monolayer sheets (ca. 1 micrometer X 1 micrometer), both suitable for cryo-electron microscopy. Images of unstained crystals embedded in ice were recorded using low-dose microscopy and analyzed by digital image processing. Both types of crystals had the same unit cell size and the same packing arrangement of PSII particles. The plane group was p22(1)2(1) and the unit cell was rectangular with dimensions of 16.7 nm X 15.3 nm containing four monomers (two face-up and two face-down). SDS-PAGE and immunoblot analyses of the 2D crystal indicated that the constituent subunits of particles in the 2D were CP47, D1, D2, cytochrome b-559 and psbI protein. A projection map of 20 A resolution revealed that each monomer has asymmetrical shape with a length of 8.1 nm and a maximal width of 7.5 nm consisting of four areas of density. Two high-density areas with similar sizes were located close to each other to form a roughly rectangular core of 4.0 nm X 6.5 nm. From its size similarity to the size of the L/M heterodimer of the bacterial reaction center, this high density core area was tentatively assigned to the D1/D2 heterodimer. The remaining large and small areas were also tentatively assigned to CP47 and cytochrome b-559 plus psbI protein respectively.
J Mol Biol 1996 Mar 29
PMID:Two-dimensional crystallization and cryo-electron microscopy of photosystem II. 860 19

Sarcoplasmic reticulum (SR) membrane vesicles derived from human atrium were characterized by specific ryanodine binding assay and fused into planar lipid bilayers. The tritiated form of the alkaloid bound to its receptor with a K(D) of 2.2 nM and a Bmax of 268 fmol/mg protein respectively. Special emphasis was placed on an anion-selective channel present in the SR membrane, which exhibited a mean conductance value of 67 pS when recorded in asymmetrical 50 mM trans/250 mM cis CsCl buffer system and a sensitivity to SITS (1 to 100 microM). Single and multiple channel activities displayed low voltage sensitivity and variability in its gating behavior which might result in spontaneous channel inactivation. However, the majority of the recordings (60%) resulted in a steady-state high open probability. The inactivated channel could be transiently reactivated with depolarizing voltage steps. This behavior is very similar, if not identical, to that observed for the SR Cl- channel in ventricular cells. The inactivation process is probably not directly related to a phosphorylation/dephosphorylation mechanism since PKA and PKG in presence of an adequate phosphorylation cocktail failed to reactivate the SR Cl- channel. In contrast, the use of a monoclonal anti-phospholamban antibody allowed the inhibition of the activity of the anionic channels. These results suggest that the regulation of the human atrial SR Cl- channel is dependent upon an interaction with phospholamban, which was clearly identified in our atrial preparations by Western blot analysis using monoclonal antibody.
J Mol Cell Cardiol 1996 Apr
PMID:Biochemical regulation of sarcoplasmic reticulum Cl- channel from human atrial myocytes: involvement of phospholamban. 873 4


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