Substrate Specificities of Variants of Barley (1,3)- and (1,3;1,4)-β-d-Glucanases Resulting from Mutagenesis and Segment Hybridization.

Barley (1,3;1,4)-β-d-glucanase is believed to have evolved from an ancestral monocotyledon (1,3)-β-d-glucanase, enabling the hydrolysis of (1,3;1,4)-β-d-glucans in the cell walls of leaves and germinating grains. In the present study, we investigated the substrate specificities of variants of the barley enzymes (1,3;1,4)-β-d-glucan endohydrolase [(1,3;1,4)-β-d-glucanase] isoenzyme EII (EII) and (1,3)-β-d-glucan endohydrolase [(1,3)-β-d-glucanase] isoenzyme GII (GII) obtained by protein segment hybridization and site-directed mutagenesis. Using protein segment hybridization, we obtained three variants of EII in which the substrate specificity was that of a (1,3)-β-d-glucanase and one variant that hydrolyzed both (1,3)-β-d-glucans and (1,3;1,4)-β-d-glucans; the wild-type enzyme hydrolyzed only (1,3;1,4)-β-d-glucans.

Evolutionary Dynamics of the Cellulose Synthase Gene Superfamily in Grasses.

Phylogenetic analyses of cellulose synthase (CesA) and cellulose synthase-like (Csl) families from the cellulose synthase gene superfamily were used to reconstruct their evolutionary origins and selection histories. Counterintuitively, genes encoding primary cell wall CesAs have undergone extensive expansion and diversification following an ancestral duplication from a secondary cell wall-associated CesA. Selection pressure across entire CesA and Csl clades appears to be low, but this conceals considerable variation within individual clades.

Geometric dependence of the conductance drop in a nanopore due to a particle.

We study the effect of a neutral particle on the ionic flow through a nanopore using a basic uniform field theory and the coupled Poisson-Nernst-Planck and Navier-Stokes (PNP-NS) equations. We consider hourglass and cylindrical pore profiles and examine how the difference in pore shape changes the position dependence of the current change due to the particle. Good quantitative agreement between both calculations is seen, though we find that the simple theory is unable to correctly capture the change in the access resistance of the pore if a particle is placed at the pore entrance.

Cortically restricted production of IP3 leads to propagation of the fertilization Ca2+ wave along the cell surface in a model of the Xenopus egg.

The fertilization Ca2+ wave in Xenopus laevis is a single, large wave of elevated free cytosolic Ca2+ concentration that emanates from the point of sperm-egg fusion and traverses the entire diameter of the egg. This phenomenon appears to involve an increase in inositol-1,4,5-trisphosphate (IP3) resulting from interaction of the sperm and egg, which then results in the activation of the endoplasmic reticulum Ca2+ release machinery. We have proposed models based on a static elevated distribution of IP3, and dynamic [IP3], however, these models have suggested that the fertilization wave passes through the center of the egg.