Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two new 2-D crystal forms of the Escherichia coli chaperone GroEL (cpn60) 2 x 7-mer have been produced using the negative staining-carbon film (NS-CF) technique. These 2-D crystals, which contain the cylindrical GroEL in side-on and end-on orientations, both possess p21 symmetry, with two molecules in the respective unit cells. The crystallographically averaged images correlate well with those obtained by other authors from single particle analysis of GroEL and our own previous crystallographic analysis. 2-D crystallization of the smaller chaperone GroES (cpn10) 7-mer has also been achieved using the NS-CF technique. Crystallographically averaged images of GroES single particle images indicate considerable variation in molecular shape, which is most likely due to varying molecular orientation on the carbon support film. The quaternary structure of GroES does, nevertheless, approximate to a ring-like shape. The complex formed by GroEL and GroES in the presence of ATP at room temperature has been shown to possess a symmetrical hollow ellipsoidal conformation. This symmetrical complex forms in the presence of a 2:1 or greater molar ratio of GroES:GroEL. At lower molar ratios linear chains of GroEL form, apparently linked by GroES in a 1:1 manner, which provide supportive evidence for the ability of both ends of the GroEL cylinder to interact with GroES. The apparent discrepancy between our data and that of other groups who have described an asymmetrical "bullet-shaped" (holo-chaperone) GroEL/ES complex is discussed in detail.
 ...
PMID:Transmission electron microscopy of GroEL, GroES, and the symmetrical GroEL/ES complex. 798 48

The sequence of the omp1 gene coding for the 40-kDa outer membrane protein (OMP) of the Gram- oral bacterium, Fusobacterium nucleatum strain Fev1, has been determined. Degenerate oligodeoxyribonucleotide primers were used to prime the amplification of a 120-mer sequence of the gene. This sequence was successively used for constructing new primers applied in asymmetrical, symmetrical, and inverse polymerase chain reaction using as template genomic DNA, self-ligated DNA fragments, or fragments ligated into either pGEM-7Zf+ or pACYC184. The codon usage of the gene was unusual in that A or T was used as the third base in the codon triplets in all cases, except for those amino acids (aa) which have only one or two possible codon choices. Only 35 of the 61 sense codons were used. The aa sequence of the protein was deduced; it consisted of 348 aa (M(r) 39,954), which is in good agreement with the 40-kDa size estimated from electrophoretic analyses. The mature protein was preceded by a 20-aa signal peptide.
 ...
PMID:Complete sequence of omp1, the structural gene encoding the 40-kDa outer membrane protein of Fusobacterium nucleatum strain Fev1. 840 32

Monosubstituted [M(N)Cl(2)(POP)] [M = Tc, 1; Re, 2] and [M(N)Cl(2)(PNP)] [M = Tc, 3; Re, 4] complexes were prepared by reaction of the precursors [M(N)Cl(4)](-) and [M(N)Cl(2)(PPh(3))(2)] (M = Tc, Re) with the diphosphine ligands bis(2-diphenylphosphinoethyl)ether (POP) and bis(2-diphenylphosphinoethyl)methoxyethylamine (PNP) in refluxing dichloromethane/methanol solutions. In these compounds, the diphosphine acted as a chelating ligand bound to the metal center through the two phosphorus atoms. Considering also the weak interaction of the heteroatom (N or O) located in the middle of the carbon backbone connecting the two P atoms, we found that the coordination arrangement of the diphosphine ligand could be viewed as either meridional (m) or facial (f), and the resulting geometry as pseudooctahedral. The heteroatom of the diphosphine ligand was invariably located trans to the nitrido linkage, as established by X-ray diffraction analysis of the representative compounds 2m and 4f. Density functional theoretical calculations showed that in POP-type complexes the mer form is favored by approximately 6 kcal mol(-1), whereas mer and fac isomers are almost isoenergetic in PNP-type complexes. A possible role of noncovalent interactions between the phosphinic phenyl substituents in stabilizing the fac-isomer was also highlighted. The existence of fac-mer isomerism in this class of complexes was attributed to the strong tendency of the two phosphorus atoms to occupy a reciprocal trans-position within the pseudooctahedral geometry. The switching of P atoms between cis- and trans-configurations was confirmed by the observation that the fac isomers, 1f and 2f, were irreversibly transformed, in solution, into the corresponding mer isomers, 1m and 2m, thus suggesting that fac complexes are more reactive species. Theoretical calculations supported this view by showing that the lowest unoccupied orbitals of the fac isomers are more accessible to a nucleophilic attack with respect to those of the mer ones. Furthermore, the large participation of the Cl orbitals to the HOMO, which is a metal-ligand pi* antibonding in the complex basal plane, shows that the Tc-Cl bonds are labile. As a consequence, facial isomers could be considered as highly electrophilic intermediates that were selectively reactive toward substitution by electron-rich donor ligands. Experimental evidence was in close agreement with this description. It was found that fac-[M(N)Cl(2)(PXP)] complexes easily underwent ligand-exchange reactions with bidentate donor ligands such as mercaptoacetic acid (NaHL(1)), S-methyl 2-methyldithiocarbazate (H(2)L(2)), diethyldithiocarbamate sodium salt (NaL(3)), and N-acetyl-L-cysteine (H(2)L(4)) to afford stable asymmetrical heterocomplexes of the type fac-[M(N)(L(n))(POP)](+/0) (5-8) and fac-[M(N)(L(n))(PNP)](+/0) (9-14) comprising two different polydentate chelating ligands bound to the same metal center. In these reactions, the bidentate ligand replaced the two chloride atoms on the equatorial plane of the distorted octahedron, leaving the starting fac-[M(N)(PXP)](2+) (X = O, N) moieties untouched. No formation of the corresponding symmetrical complexes containing two identical bidentate ligands was detected over a broad range of experimental conditions. Solution-state NMR studies confirmed that the structure in solution of these heterocomplexes was identical to that established in the solid state by X-ray diffraction analysis of the prototype complexes fac-[M(N)(HL(2))(POP)][BF(4)] [M = Tc, 7; Re, 8] and fac-[Tc(N)(HL(2))(PNP)][BF(4)], 11. In conclusion, the novel metal fragment fac-[M(N)(PXP)](2+) could be utilized as an efficient synthon for the preparation of a large class of asymmetrical, nitrido heterocomplexes incorporating a particular diphosphine ligand and a variety of bidentate chelating molecules.
 ...
PMID:Chemistry of the strong electrophilic metal fragment [(99)Tc(N)(PXP)](2+) (PXP = diphosphine ligand). A novel tool for the selective labeling of small molecules. 1223 61

The biologically active state of many proteins requires their prior homo-oligomerisation. Such complexes are typically symmetrical, a feature that has been proposed to increase their stability and facilitate the evolution of allosteric regulation. We wished to examine the possibility that similar structures and properties could arise from genetic amplifications leading to internal symmetrical repeats. For this, we identified internal structural repeats in a nonredundant Protein Data Bank subset. While testing if repeats in proteins tend to be symmetrical, we found that about half of the large internal repeats are symmetrical, most frequently around a rotation axis of 180 degrees . These repeats were most likely created by genetic amplification processes because they show significant sequence similarity. Symmetrical repeats tend to have a fixed number of copies corresponding to their rotational symmetry order, that is, two for 180 degrees rotation axis, whereas asymmetrical repeats are in longer proteins and show copy number variability. When possible, we confirmed that proteins with symmetrical repeats folding as an n-mer have homologues lacking the repeat with a higher oligomerisation number corresponding to the rotation symmetry order of the repeat. Phylogenetic analyses of these protein families suggest that typically, but not always, symmetrical repeats arise in one single event from proteins that are homo-oligomers. These results suggest that oligomerisation and amplification of internal sequences can interplay in evolutionary terms because they result in functional analogues when the latter exhibit rotational symmetry.
 ...
PMID:Alternative to homo-oligomerisation: the creation of local symmetry in proteins by internal amplification. 1976 88

When the micellar aggregation number (Nagg) is sufficiently small (Nagg < 30), the micelle shows an abnormal aggregation behavior: monodispersity without any distribution in Nagg, whose values coincide with the vertex number of a regular polyhedral structure, i.e., they are termed Platonic solids. Micelles with these characteristics are named "Platonic micelles". In this study, we investigated the aggregation behavior of calixarene-based micelles bearing primary amines-the first example of Platonic micelles-with increasing alkyl chain length by small-angle X-ray scattering, asymmetrical flow field flow fractionation coupled with multiangle light scattering, and analytical ultracentrifugation measurements. Morphological transition of the micelles from spherical to cylindrical was observed when the alkyl chain length was increased in this calixarene-based micellar system, which is similar to the case of conventional systems and is acceptable in terms of the packing parameter principle. However, although the micellar Nagg normally increases with an increase in the alkyl chain length, the structure of calixarene-based Platonic micelles bearing butyl (C4), heptyl (C5), and hexyl (C6) chains remains at 12-mer. This is presumably due to the relationship between the thermodynamic stability of the Platonic micelles and the coverage ratio defined by the Tammes problem.
 ...
PMID:Non-dependence of dodecamer structures on alkyl chain length in Platonic micelles. 3082 7