Cell surface beta-1,4-galactosyltransferase is associated with the detergent-insoluble cytoskeleton on migrating mesenchymal cells.

Cell surface beta-1,4-galactosyltransferase (GalTase) partially mediates a variety of cell interactions with laminin-containing matrices, including mesenchymal cell spreading and migration and neurite initiation, by binding to N-linked oligosaccharides within the E8 domain of laminin. Previous studies using indirect immunofluorescence have suggested that some surface GalTase colocalizes with actin-containing microfilaments in migrating cells. In this study, we present more direct biochemical evidence showing that surface GalTase is associated with the detergent-insoluble cytoskeleton and that this association is dependent upon the integrity of the cytoskeleton, valency of the anti-GalTase antibody, and migratory status of the cell. Two-thirds of the surface GalTase was associated with the detergent-insoluble cytoskeleton when assayed either by monovalent anti-GalTase Fab fragments or by extracting any detergent-soluble GalTase prior to labeling with intact anti-GalTase IgG. However, 80-100% of the surface GalTase could be induced to associate with the cytoskeleton when cross-linked with anti-GalTase IgG prior to detergent extraction. Destabilizing cytoskeleton-protein interactions with high levels of KCl, elevated pH, or cytochalasin B reduced the amount of surface GalTase retained in the detergent-insoluble cytoskeleton fraction. Finally, we have shown previously that laminin induces the expression of GalTase onto lamellipodia of migrating cells, and in this study, we show that the laminin-induced increase in surface GalTase is cytoskeletally associated. Collectively, these data suggest that cell surface GalTase participates in cell spreading and migration on laminin by virtue of its association with the cytoskeleton.     

Inhibition of the restriction endonuclease BanII using modified DNA substrates. Determination of phosphate residues critical for the formation of an active enzyme-DNA complex

The restriction endonuclease BanII catalyzes the cleavage of double-stranded DNA and recognizes the degenerate sequence 5'-GPuGCPyC-3'. The poly-linker of M13mp18 contains one such sequence, 5'-GAGCTC-3'. The three other possible sites recognized by the enzyme were prepared by site-directed muta-genesis. The substitution of phosphate groups by phosphorothioate residues at some positions within the various recognition sites had relatively little effect on the rate of cleavage of the DNA. However, when the DNA contained a phosphorothioate group at the site of cleavage the rate of linearization of the DNA was decreased by a factor of 9. Interestingly, DNA which contained an additional phosphorothioate internucleotidic linkage immediately 3'-outside the recognition site could not be linearized by the enzyme. The results indicate that an important contact between enzyme and substrate is perturbed by the presence of the sulfur atom at this position.     

The base catalysed anomerisation of β-5-formyluridine; crystal and molecular structure of α-5-formyluridine

On treatment with strong base β-5-formyluridine undergoes an anomerisation to give a mixture of the α- and β-anomers. The anomers have been separated by fractional recrystallisation and the absolute configuration of the α-anomer has been determined by X-ray analysis.     

Immigration,remittances, and transnational social capital formation: a Cuban case study

Social capital takes on distinctive meaning in the context of large-scale immigration from poor to rich countries. In this article, characteristics of social capital embedded in transnational networks and norms, conditions conducive to the formation of such networks, and effects such networks have are extrapolated from an analysis of how and why cross-border relations among Cuban-Americans and Cubans in their homeland have changed since the 1959 Castro-led revolution. The transnational social capital generating benefit on which the study focuses is remittances. Remittances are of growing global importance to less developed countries, and in some countries they generate more revenue than foreign aid and foreign investment. The analysis addresses a range of unintended as well as intended consequences remittances may have.     

Auxin and chloroplast movements

Auxin is involved in a wide spectrum of physiological processes in plants, including responses controlled by the blue light photoreceptors phototropins: phototropic bending and stomatal movement. However, the role of auxin in phototropin‐mediated chloroplast movements has never been studied. To address this question we searched for potential interactions between auxin and the chloroplast movement signaling pathway using different experimental approaches and two model plants, Arabidopsis thaliana and Nicotiana tabacum. We observed that the disturbance of auxin homeostasis by shoot decapitation caused a decrease in chloroplast movement parameters, which could be rescued by exogenous auxin application. In several cases, the impairment of polar auxin transport, by chemical inhibitors or in auxin carrier mutants, had a similar negative effect on chloroplast movements. This inhibition was not correlated with changes in auxin levels. Chloroplast relocations were also affected by the antiauxin p‐chlorophenoxyisobutyric acid and mutations in genes encoding some of the elements of the SCF^TIR1‐Aux/IAA auxin receptor complex. The observed changes in chloroplast movement parameters are not prominent, which points to a modulatory role of auxin in this process. Taken together, the obtained results suggest that auxin acts indirectly to regulate chloroplast movements, presumably by regulating gene expression via the SCF^TIR1‐Aux/IAA‐ARF pathway. Auxin does not seem to be involved in controlling the expression of phototropins.