Nucleotide sequence of the lipase gene lip3 from the antarctic psychotroph Moraxella TA144

A lipase gene (lip3) from the psychotrophic strain Moraxella TA144 has been cloned and sequenced. The deduced primary structure of the lipase preprotein is composed of 315 amino acids with a predicted Mr of 34,772. This enzyme contains two consensus peptides showing cluster of glycine residues that may be involved in domain flexibility. The cloned gene product conserves the low temperature activity and the thermolability properties of the wild enzyme.     

Primary Herbivory by Wood-Boring Insects along an Architectural Gradient of Rhizophora mangle

We investigated the distribution of primary xylovores in Rhizophora mangle (red mangrove) first-order branches, i.e., “twigs”, along an architectural gradient on Belizean mangrove cays. Greater structural diversity in R. mangle architecture, xylovore availability, occurrence of natural enemies, and habitat do not result in variable xylovore species richness. Despite large differences in architectural complexity, tall, fringe, dwarf, and sapling trees host the same set of primary wig borers. However, tall trees support greater diversity and abundance of twig inquilines than other tree forms. Primary twig borers have a key role in structuring these mangrove communities because their galleries and pupal chambers provide habitats for numerous species of secondary xylovores and inquilines. We also measured the amount of leaf area removed from R. mangle's canopy by wood- and leaf-feeding herbivores. Vigorously growing tall and sapling trees sustain greater losses because of twig borers than dwarf trees. However, xylovory in fringe trees was not different from any of the other categories. Cumulative herbivory was greatest in the tall trees. In most cases, leaf-area loss as an indirect or collateral result of primary xylovory equaled or exceeded leaf-area loss as a direct result of folivory.     

Leaf Proteolytic Activities and Senescence during Grain Development of Field-grown Corn (Zea mays L.)

Some proteolytic enzymes occurring in the leaves of field-grown corn (Zea mays) (B73) were identified and partially characterized. Changes in activities of several proteolytic enzymes and in concentrations of protein and chlorophyll as a function of intraleaf segments (tip to base), leaf position, and leaf senescence during grain development and maturation were followed in crude leaf extracts.     

High and low affinity binding sites for Concanavalin A on normal human fibroblasts in vitro

The binding of high specific activity, radioactive Concanavalin A to cultured normal human fibroblasts was investigated. We report the presence of two classes of Concanavalin A binding sites on the plasma membranes of these cells. These classes of binding sites are distinguished by their affinities for the lectin. Scatchard analysis of the binding data indicates the presence of a class of high affinity sites which are saturated at about 0.25 μg/ml of Concanavalin A. The other, lower affinity binding sites are not saturated until 50–100 μg/ml Concanavalin A levels are achieved. At 4°C the K_a for the high affinity sites varies between 1.5 – 5 × 10⁹ M^?1 depending on the method used to label the Concanavalin A. For the lower affinity sites K_a varies between 1 – 4 × 10⁶ M^?1. The average number of high affinity sites per cell is 8 × 10⁵ representing less than 1% of the total receptor sites for the lectin.     

1-substituted tetrahydroisoquinoline analogs: beta adrenoceptor blocking agents in the isolated perfused rabbit heart.

The 1-benzyl and 1-methyl congeners of trimetoquinol were tested for antagonism of receptors which mediate inotropy and chronotropy in the isolated perfused rabbit heart. 1-Benzyltrimetoquinol was found to be a blocker of resting, isoproterenol- and dobutamine-stimulated inotropy at concentrations (10^?7?10^?5M) which did not significantly affect chronotropy ( > 10^?5M). 1-Methyltrimetoquinol was found to be a partial agonist in the resting myocardium, weakly blocking inotropy and chronotropy at doses of 10^?7?10^?5M. At a concentration of 10^?4M, 1-methyltrimetoquinol was an agonist of both chronotropy and inotropy. These stimulatory properties appear to be direct (not affected by prior reserpinization) and antagonized by propranolol. In the isoproterenol-stimulated heart, 1-methyltrimetoquinol was a specific negative inotropic agent at doses (10^?7?10^?5M) above which agonist properties were manifest. At 10^?4M, 1-methyltrimetoquinol acted synergistically with isoproterenol to produce positive inotropy and chronotropy significantly greater than that of isoproterenol alone. Currently, it is believed that the receptors which mediate inotropy and chronotropy are $\text{beta}$ adrenergic in nature. Thus, it would appear that 1-benzyltrimetoquinol is a specific antagonist of those $\text{beta}$-receptors which mediate inotropy, while 1-methyltrimetoquinol is a partial agonist of both inotropic and chronotropic $\text{beta}$-receptors. Further, the response to these compounds does not appear to be proportionate in various regions of the myocardium.     

Dual regulation of the synthesis of the arginine pathway carbamoylphosphate synthase of Saccharomyces cerevisiae by specific and general controls of amino acid biosynthesis.

Summary The synthesis of the arginine pathway carbamoylphosphate synthase (CPSase A) of Saccharomyces cerevisiae is subject to two control mechanisms. One mechanism is specific for CPSase A and is exerted by arginine; it probably involves a repressoroperator type of interaction. This specific mechanism regulates the expression of gene cpaI coding for the small glutaminase subunit of CPSase A but has little influence on the production of the large subunit of the enzyme, a product of gene cpaII. This large component, which alone has no biological significance, accumulates freely under conditions of arginine repression. The second mechanism is general: it controls enzyme synthesis in a number of amino acid biosynthetic pathways in addition to the arginine sequence. Two types of evidence that this general mechanism participates in the control of CPSase A synthesis are presented: (1) Derepression upon starvation for any amino acid of which the synthesis is subject to this general control; and (2) repression during growth in amino acid-rich medium. In contrast to the specific mechanism, the general mechanism regulates the expression of both the cpaI and cpaII genes.     

Expression of Psychrophilic Genes in Mesophilic Hosts: Assessment of the Folding State of a Recombinant α-Amylase

α-Amylase from the antarctic psychrophile Alteromonas haloplanktis is synthesized at 0 ± 2°C by the wild strain. This heat-labile α-amylase folds correctly when overexpressed in Escherichia coli, providing the culture temperature is sufficiently low to avoid irreversible denaturation. In the described expression system, a compromise between enzyme stability and E. coli growth rate is reached at 18°C.