Interaction of adenylic acid with alkaline earth metal ions in the crystalline solid and aqueous solution. Evidence for the sugar C'2-endo/anti, C'3-endo/anti and C'4-exon/anti conformational changes

The reaction of adenosine 5'-monophosphoric acid (H2-AMP) with the alkaline earth metal ions has been investigated in aqueous solution at neutral pH. The solid salts of Mg-AMP.5H2O, Ca-AMP.6H2O, Sr-AMP.7H2O and Ba-AMP.7H2O were isolated and characterized by Fourier transform infrared, 1H-NMR spectroscopy and X-ray powder diffraction measurements. Spectroscopic and other evidence showed that the Sr-AMP.7H2O and Ba-AMP.7H2O are isomorphous, whereas the Mg-AMP.5H2O and Ca-AMP.6H2O are not similar. The Mg2+ binding is through the N-7 (inner-sphere) and the phosphate group (outer-sphere via H2O), while the Ca2+ binds to the phosphate group (inner-sphere) and to the base N-7 site (outer-sphere through H2O). The Sr2+ and Ba2+ bind to H2O molecules, H-bonding to the N-7, N-1 and the phosphate group (outer-sphere). In aqueous solution, an equilibrium between the inner- and outer-sphere metal ion bindings can be established. The sugar moiety exhibited C'2-endo/anti conformation, in the free H2-AMP acid and the magnesium salt, C'3-endo/anti in the calcium salt and unusual C'4-exo/anti, in the strontium and barium salts.     

Studies of helix fraying and solvation using 13C' isotopomers

Both NMR and IR studies of carbonyl (13C') isotopomers of designed helices can provide residue-level details regarding the fractional occurrence and melting behavior of helical phi/psi angles along the sequence of helical peptides, details that cannot be obtained from CD or 1H-NMR studies. We have studied a classic series of helical models, Ac-YGG-(KAXAA)3K-NH2 (X=A,V), in both aqueous and helix-favoring media containing fluoroalcohol cosolvents, including a solvent system allowing the observation of cold denaturation. These studies confirmed the strong N-capping associated with this sequence and revealed more extensive C-terminal fraying than that calculated using current helicity prediction algorithms. In the X=A series, the central residues are somewhat resistant to thermal melting; it instead occurs predominantly at the frayable C terminus. For the X=V series under cold-denaturing conditions, the temperature of maximal helicity is not uniform along the sequence and both solvated and nonsolvated helical alanine sites (13C=O stretches at 1592 cm(-1) and 1615 cm(-1), respectively) are apparent. Correlation between the two spectroscopies employed yielded the intriguing observation that the valine side chain is able to desolvate the i - 4 amide in short monomeric helices. In addition, we report further measurements of the temperature dependence of alanine statistical coil chemical shifts, the temperature dependence of the 13C chemical shift of urea (employed as chemical shift reference), and a useful formula for converting 13C' shifts into fractional helicities.     

Poliovirus 2A(pro) induces the nucleic translocation of poliovirus 3CD and 3C' proteins

Poliovirus genomic RNA replication, protein translation, and virion assembly are performed in the cytoplasm of host cells. However, this does not mean that there is no relationship between poliovirus infection and the cellular nucleus. In this study, recombinant fluorescence-tagged poliovirus 3CD and 3C' proteins were shown to be expressed mainly in the cytoplasm of Vero cells in the absence of other viral proteins. However, upon poliovirus infection, many of these proteins redistributed to the nucleus, as well as to the cytoplasm. A series of transfection experiments revealed that the poliovirus 2A(pro) was responsible for the same redistribution of 3CD and 3C' proteins to the nucleus. Furthermore, a mutant 2A(pro) protein lacking protease activity abrogated this effect. The poliovirus 2A(pro) protein was also found to co-localize with the Nup153 protein, a component of the nuclear pore complexes on the nuclear envelope. These data provide further evidence that there are intrinsic interactions between poliovirus proteins and the cell nucleus, despite that many processes in the poliovirus replication cycle occur in the cytoplasm.     

Efficient RNA 2'-O-methylation requires juxtaposed and symmetrically assembled archaeal box C/D and C'/D' RNPs

Box C/D ribonucleoprotein (RNP) complexes direct the nucleotide-specific 2'-O-methylation of ribonucleotide sugars in target RNAs. In vitro assembly of an archaeal box C/D sRNP using recombinant core proteins L7, Nop56/58 and fibrillarin has yielded an RNA:protein enzyme that guides methylation from both the terminal box C/D core and internal C'/D' RNP complexes. Reconstitution of sRNP complexes containing only box C/D or C'/D' motifs has demonstrated that the terminal box C/D RNP is the minimal methylation-competent particle. However, efficient ribonucleotide 2'-O-methylation requires that both the box C/D and C'/D' RNPs function within the full-length sRNA molecule. In contrast to the eukaryotic snoRNP complex, where the core proteins are distributed asymmetrically on the box C/D and C'/D' motifs, all three archaeal core proteins bind both motifs symmetrically. This difference in core protein distribution is a result of altered RNA-binding capabilities of the archaeal and eukaryotic core protein homologs. Thus, evolution of the box C/D nucleotide modification complex has resulted in structurally distinct archaeal and eukaryotic RNP particles.     

C'3 polymorphism of human complement in North-East England.

The C'3 polymorphism of human complement was investigated in a sample of 268 unrelated individuals in North-East England. The two common genes were comparable in frequency with other European populations investigated so far. Two individuals were found to have rare variant C'3 types.     

Polymorphism of C'3 in German,Bulgarian, Iranian and Angola population

Summary Using agarose gel electrophoresis, C'3 was typed in 4 populations. The gene frequencies of the common allele C'3^S in these 4 populations were Germans (0.8071), Bulgarians (0.8149), Iranians (0.7920) and Angola (0.9532). The results are discussed.

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Zusammenfassung Auf Grund der Aarosegel-Elektrophorese erfolgte die C'3-Bestimmung bei 4 Populationen. Die Genfrequenzen der bekannten Allele C'3^S in diesen 4 Populationen waren von Deutschen (0,8071), Bulgaren (0,8149), Iranern (0,7920) und Negern (Angola, 0,9532). Die Ergebnisse werden diskutiert.