Difference in the hydration water mobility around F-actin and myosin subfragment-1 studied by quasielastic neutron scattering

Hydration water is essential for a protein to perform its biological function properly. In this study, the dynamics of hydration water around F-actin and myosin subfragment-1 (S1), which are the partner proteins playing a major role in various cellular functions related to cell motility including muscle contraction, was characterized by incoherent quasielastic neutron scattering (QENS). The QENS measurements on the D₂O- and H₂O-solution samples of F-actin and S1 provided the spectra of hydration water, from which the translational diffusion coefficient (D_T), the residence time (τ_T), and the rotational correlation time (τ_R) were evaluated. The D_T value of the hydration water of S1 was found to be much smaller than that of the hydration water of F-actin while the τ_T values were similar between S1 and F-actin. On the other hand, the τ_R values of the hydration water of S1 was found to be larger than that of the hydration water of F-actin. It was also found that the D_T and τ_R values of the hydration water of F-actin are similar to those of bulk water. These results suggest a significant difference in mobility of the hydration water between S1 and F-actin: S1 has the typical hydration water, the mobility of which is reduced compared with that of bulk water, while F-actin has the unique hydration water, the mobility of which is close to that of bulk water rather than the typical hydration water around proteins.     

Penicillin-binding proteins in Mycobacterium smegmatis

Abstract The penicillin-binding proteins (PBPs) of Mycobacterium smegmatis were studied. Five PBPs ranging in M _r from approx. 114000 to 25000 were detected in the cytoplasmic membrane. The affinities of the PBPs for selected β-lactam antibiotics were determined. Most of the antibiotics bound to PBPs 3 and 4 at low concentrations. A penicillin-susceptible mutant and a cefmetazole-resistant mutant were isolated by selection in vitro. The PBPs of these mutants were identical to those of the parent strain. The affinity of cefmetazole for the individual PBPs was identical in each mutant.     

Polysaccharides of the cellular slime mold II. Change of intra- and extracellular polysaccharides during growth phase of Dictyostelium discoideum NC-4

The three intra- and extracellular polysaccharide fractions were isolated during the growth phase of Dictyostelium discoideum NC-4, and the change in content of component sugars of four fractions during the culture period was examined. Myxamoebae most extensively contain a polysaccharide fraction extracted with phenol-water (polysaccharide fraction I) in a quantity of about 15–23% per dry cell. After 15 h the uronic acid formed in the polysaccharide fraction I, and the cell, could be aggregated. The glucosamine content in the polysaccharide fraction I reached a maximum as the myxamoebae entered the exponential phase, and a large amount of galactose was produced as the cell entered the stationary phase. The phenol-water extract from the cells of the stationary phase was reacted with concanavalin-A.     

Papillary projections at the lingual margin in the striped dolphin,Stenella coeruleoalba,with Special Reference to Their Development and Regression

Papillary projections along the anterolateral margin of the tongue were observed in fetal and young stages of the striped dolphin, Stenella coeruleoalba. Papillary projections appear in the prenatal period and attain maximum development in the early postnatal period. They almost disappear by weaning. Vestigial eminences remain at the corresponding region, but they completely disappear in the adult. The papillary projections observed differ markedly from the lingual papillae of the general mammalian tongue as they are temporary, localized at the anterolateral margin and large in size. The projections were also present in young individuals of some other dolphins. No taste buds could be seen on the projections in any of the stages of all specimens observed. Such projections may have important mechanical functions during suckling in these mammals.