Cloning and characterization of a sucrase from Leuconostoc mesenteroides

A sucrase gene from Leuconostoc mesenteroides was cloned and expressed in Escherichia coli. The cloned enzyme did not show dextransucrase or sucrose phosphorylase activity. HPLC and GC-MS analyses of the sucrase products indicated the presence of fructose and glucose in equimolar amounts. IPTG induction did not increase sucrase activity in E. coli indicating that the cloned gene may be transcribed from its own promoter. To our knowledge, this is the first sucrase cloned from L. mesenteroides that has invertase activity.     

Analysis of mutations in cyclodextrin glucanotransferase from Bacillus stearothermophilus which affect cyclization characteristics and thermostability.

Cyclodextrin glucanotransferase (CGTase; EC 2.4.1.19) produces cyclodextrin from starch. The CGTase molecule is composed of four globular domains, A, B, C, and D. In order to gain better understanding of the amylolytic and cyclization mechanisms of CGTase, mutant CGTases were constructed from a CGTase gene (cgt1) of Bacillus stearothermophilus NO2. Cgt1-F191Y (Phe at position 191 was replaced by Tyr), Cgt1-F191Y-F255Y, Cgt1-W254V-F255I, Cgt1-W254V, and Cgt1-F255I were constructed for the analysis of the NH2-terminal region. It was revealed that amino acids surrounding a spiral amylose are important for cyclization characteristics and that hydrophobic amino acids just after the Glu catalytic site play an important role in the hydrolysis characteristics of the enzyme. Mutant CGTases Cgt1-T591F and Cgt1-W629F were also constructed to study the role of a second substrate-binding site in domain D, and it was suggested that substrate binding at both domains A and D stabilized the enzyme and optimized cyclodextrin production.     

Genotype-specific interactions and the trade-off between host and parasite fitness

Background  

Evolution of parasite traits is inextricably linked to their hosts. For instance one common definition of parasite virulence is the reduction in host fitness due to infection. Thus, traits of infection must be viewed in both protagonists and may be under shared genetic and physiological control. We investigated these questions on the oomycete Hyaloperonospora arabidopsis (= parasitica), a natural pathogen of the Brassicaceae Arabidopsis thaliana.     

Dominance,Coloration, and Social and Sexual Behavior in Male Drills <Emphasis Type="Italic">Mandrillus leucophaeus</Emphasis>

Sexual selection has driven the evolution and elaboration of a wide variety of displays and ornaments in male nonhuman primates, including capes, cheek flanges, and sexual coloration. Among the most sexually dimorphic of all primates is the drill (Mandrillus leucophaeus), the males of which can be 3 times the mass of females, possess large canines, and exhibit extremely bright sexual skin coloration. However, the function of male coloration in this species has never been examined. Here, we present data on male color (measured objectively using digital photography), dominance rank, measures of male-female association, and key sexual behaviors, of adult male drills (n = 17) living in four semi free-ranging enclosures at the Drill Rehabilitation and Breeding Center in Nigeria. We test the hypothesis that male coloration is a badge of status, indicating dominance rank, and the hypothesis that male coloration attracts females. We found that male coloration did indicate rank, and that high ranking, strongly colored males were more likely to associate with adult females, and more specifically with fully tumescent females. These males also engaged in more sexual activity. However, measures of male-female association and sexual behaviors were not related to male color once rank had been taken into consideration; i.e., for males of a given rank, females did not prefer those that were more colorful. We discuss the results in light of what is known about the wild drill social system, in which unfamiliar individuals may come together in “supergroups,” and in which quality indicators of competitive ability may be particularly important.     

Stereospecific reactivation of human brain and erythrocyte acetylcholinesterase inhibited by 1,2,2-trimethylpropyl methylphosphonofluoridate (soman)

Human erythrocyte and brain acetylcholinesterase are preferentially inhibited by the P(-)-isomers of C(+/-)P(+/-)-soman. The enzymes inhibited by the P(-)-isomers behave similarly with respect to oxime-induced reactivation and aging. HI-6 is the best reactivator for C(+)P(-)-soman-inhibited acetylcholinesterases. Oxime-induced reactivation of the C(-)P(-)-soman-inhibited acetylcholinesterases is much more difficult to achieve.     

Role of membranes and energy-producing reactions in cellular processing of insulin in primary cultures of rat hepatocytes

Incubation of primary cultures of rat hepatocytes with the local anesthetics, procaine or lidocaine, had little or no effect on insulin uptake or degradation but caused an inhibition of insulin-stimulated glycogenesis. While exposure of cultures to the amines, monodansylcadaverine or CH3NH2, resulted in significant dose-dependent decreases in glycogenesis, only monodansylcadaverine (an inhibitor of receptor clustering) decreased uptake whereas CH3NH2 (a lysosomotropic agent) caused increases in both insulin uptake and degradation. When cells were treated with agents which inhibit glycolysis (NaF, 2-deoxy-D-glucose) or oxidative metabolism (2,4-dinitrophenol, carbonyl cyanide m-chlorophenyl hydrazone, NaN3, antimycin A), pronounced inhibitions of each of the bioactivities studied (syntheses of glycogen, protein, lipid) were observed, but only the glycolytic inhibitors decreased insulin uptake. These results suggest that insulin is internalized by an endocytotic process involving receptor clustering and requiring metabolic energy derived from glycolysis. The post-receptor biosynthetic processes involved in the expression of the biological activities of insulin (syntheses of glycogen, protein, lipid) require energy produced by oxidative metabolism while the degradation of insulin is carried out by nonlysosomal mechanisms which are not energy-requiring.     

Synthesis and NMR spectra of 13C-labeled coenzyme A esters

The synthesis of coenzyme A thioesters of 13C-labeled acetate, propionate, succinate, and methyl malonate is described. The average yields were 94%. The 13C-NMR spectra were determined to provide a reference for the resonance positions of these metabolites. The synthesis of coenzyme thioesters of small-molecular-weight acids labeled with 13C has not been described previously, nor have the resonance positions been previously reported.