Unexpected High Digestion Rate of Cooked Starch by the Ct-Maltase-Glucoamylase Small Intestine Mucosal α-Glucosidase Subunit

For starch digestion to glucose, two luminal α-amylases and four gut mucosal α-glucosidase subunits are employed. The aim of this research was to investigate, for the first time, direct digestion capability of individual mucosal α-glucosidases on cooked (gelatinized) starch. Gelatinized normal maize starch was digested with N- and C-terminal subunits of recombinant mammalian maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI) of varying amounts and digestion periods. Without the aid of α-amylase, Ct-MGAM demonstrated an unexpected rapid and high digestion degree near 80%, while other subunits showed 20 to 30% digestion. These findings suggest that Ct-MGAM assists α-amylase in digesting starch molecules and potentially may compensate for developmental or pathological amylase deficiencies

Diet and other environmental factors shape the bacterial communities of fish gut in an eutrophic lake

Aims The aim of this work was to study the gut microbial diversity from eight species of wild fish with different feeding habits, digestive physiology (gastric vs agastric) and provide comparative structural analysis of the microbial communities within their environment (food items, water, sediments and macrophytes). Methods and Results The microbiota of fish gut and their prey items were studied using next generation high‐throughput sequencing of the 16S ribosomal RNA genes. A scatter plot based on PCoA scores demonstrated the microbiota formed three groups: (i) stomach and intestinal mucosa (IM), (ii) stomach and intestinal content (IC), and (iii) prey and environment. Comparisons using ANOSIM showed significant differences among IC of omnivorous, zoobenthivorous, zooplanktivorous‐piscivorous fishes (P ≤ 0·1). No significant difference was detected for mucosa from the same groups (P > 0·1). Conclusions Neither the interspecies differences in fish diet nor their phylogenetic position had any effect on the microbiome of the IM, but diet did influence the composition of the microbiota of the IC. Significance and Impact of the Study The data demonstrate that fish harboured specific groups of bacteria that do not completely reflect the microbiota of the environment or prey.info:eu-repo/semantics/acceptedVersio

FRET binding antenna reports spatiotemporal dynamics of GDI-Cdc42 GTPase interactions

Guanine-nucleotide dissociation inhibitors (GDI) are negative regulators of Rho family GTPases that sequester the GTPases away from the membrane. Here we ask how GDI-Cdc42 interaction regulates localized Cdc42 activation for cell motility. The sensitivity of cells to overexpression of Rho family pathway components led us to a new biosensor design (GDI.Cdc42 FLARE), in which Cdc42 was modified with a FRET ‘binding antenna’ that selectively reported Cdc42 binding to endogenous GDI. Similar antennae could also report GDI-Rac1 and GDI-RhoA interaction. Through computational multiplexing and simultaneous imaging, we determined the spatiotemporal dynamics of GDI-Cdc42 interaction and Cdc42 activation during cell protrusion and retraction. This revealed a remarkably tight coordination of GTPase release and activation on a time scale of 10 seconds, suggesting that GDI-Cdc42 interactions are a critical component in the spatiotemporal regulation of Cdc42 activity, and not merely a mechanism for global sequestration of an inactivated pool of signaling molecules

Many roads to symmetry breaking: Molecular mechanisms and theoretical models of yeast cell polarity

Mathematical modeling has been instrumental in identifying common principles of cell polarity across diverse systems. These principles include positive feedback loops that are required to destabilize a spatially uniform state of the cell. The conserved small G-protein Cdc42 is a master regulator of eukaryotic cellular polarization. Here we discuss recent developments in studies of Cdc42 polarization in budding and fission yeasts and demonstrate that models describing symmetry-breaking polarization can be classified into six minimal classes based on the structure of positive feedback loops that activate and localize Cdc42. Owing to their generic system-independent nature, these model classes are also likely to be relevant for the G-protein–based symmetry-breaking systems of higher eukaryotes. We review experimental evidence pro et contra different theoretically plausible models and conclude that several parallel and non–mutually exclusive mechanisms are likely involved in cellular polarization of yeasts. This potential redundancy needs to be taken into consideration when interpreting the results of recent cell-rewiring studies