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71.
Jacques M Mathieu John Schloendorn Bruce E Rittmann Pedro JJ Alvarez 《Microbial cell factories》2009,8(1):21-18
Catabolic insufficiency in humans leads to the gradual accumulation of a number of pathogenic compounds associated with age-related
diseases, including atherosclerosis, Alzheimer's disease, and macular degeneration. Removal of these compounds is a widely
researched therapeutic option, but the use of antibodies and endogenous human enzymes has failed to produce effective treatments,
and may pose risks to cellular homeostasis. Another alternative is "medical bioremediation," the use of microbial enzymes
to augment missing catabolic functions. The microbial genetic diversity in most natural environments provides a resource that
can be mined for enzymes capable of degrading just about any energy-rich organic compound. This review discusses targets for
biodegradation, the identification of candidate microbial enzymes, and enzyme-delivery methods. 相似文献
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Crustacean and cheliceratan hemocyanins (oxygen-transport proteins) and
insect hexamerins (storage proteins) are homologous gene products, although
the latter do not bind oxygen and do not possess the copper- binding
histidines present in the hemocyanins. An alignment of 19 amino acid
sequences of hemocyanin subunits and insect hexamerins was made, based on
the conservation of elements of secondary structure observed in X-ray
structures of two hemocyanin subunits. The alignment was analyzed using
parsimony and neighbor-joining methods. Results provide strong indications
for grouping together the sequences of the 2 crustacean hemocyanin
subunits, the 5 cheliceratan hemocyanin subunits, and the 12 insect
hexamerins. Within the insect clade, four methionine- rich proteins, four
arylphorins, and two juvenile hormone-suppressible proteins from
Lepidoptera, as well as two dipteran proteins, form four separate groups.
In the absence of an outgroup sequence, it is not possible to present
information about the ancestral state from which these proteins are
derived. Although this family of proteins clearly consists of homologous
gene products, there remain striking differences in gene organization and
site of biosynthesis of the proteins within the cell. Because studies on
18S and 12S rRNA sequences indicate a rather close relationship between
insects and crustaceans, we propose that hemocyanin is the ancestral
arthropod protein and that insect hexamerins lost their copper-binding
capability after divergence of the insects from the crustaceans.
相似文献
76.
Natalie Saldou Preston A. Baecker Bin Li Zhengyu Yuan Rena Obernolte James Ratzliff Eric Osen Kurt Jarnagin Earl R. Shelton 《Cell biochemistry and biophysics》1998,28(2-3):187-217
Individual isozymes of family four cyclic-nucleotide phosphodiesterases (PDE-4s) were characterized and compared in order
to advance our understanding of how PDE-4s regulate cAMP levels in cells. Full-length and shorter clones containing various
functional domains were constructed and overexpressed using a recombinant baculovirus-infected Sf9 insect cell system. One
form each of PDE-4C and 4D was purified 125- and 534-fold, respectively, using anion-exchange and affi-gel blue chromatography.
The purified material was unaltered in size on SDS-polyacrylamide gels during purification and nearly homogeneous (>95%) as
estimated by both staining and immunoblotting. Approximately 1 mg of PDE-4D (74.7 kDa) and 3.7 mg of PDE-4C (61.4 kDa) could
be isolated from a 6-L culture of cells. The physical characteristics of Stokes' radius and sedimentation coefficient for
PDE-4 enzymes cloned from each of the four isogenes were determined using size-exclusion chromatography and sedimentation
in glycerol gradients. Calculations indicate that both long and short forms can form dimers, although evidence for monomers
and higher-order subunit association was seen. Furthermore, the results clearly show that all long and short forms of PDE-4
are highly asymmetric molecules. This work has shown that large amounts of PDE-4 proteins can be purified and characterized
physically and enzymatically to yield information that will enable a greater understanding of how PDE-4 enzymes function in
cells. 相似文献
77.
Interactions of Photobleaching and Inorganic Nutrients in Determining Bacterial Growth on Colored Dissolved Organic Carbon 总被引:8,自引:0,他引:8
Abstract Bacteria are key organisms in the processing of dissolved organic carbon (DOC) in aquatic ecosystems. Their growth depends on both organic substrates and inorganic nutrients. The importance of allochthonous DOC, usually highly colored, as bacterial substrate can be modified by photobleaching. In this study, we examined how colored DOC (CDOC) photobleaching, and phosphorus (P) and nitrogen (N) availability, affect bacterial growth. Five experiments were conducted, manipulating nutrients (P and N) and sunlight exposure. In almost every case, nutrient additions had a significant, positive effect on bacterial abundance, production, and growth efficiency. Sunlight exposure (CDOC photobleaching) had a significant, positive effect on bacterial abundance and growth efficiency. We also found a significant, positive interaction between these two factors. Thus, bacterial use of CDOC was accelerated under sunlight exposure and enhanced P and N concentrations. In addition, the accumulation of cells in sunlight treatments was dependent on nutrient availability. More photobleached substrate was converted into bacterial cells in P- and N-enriched treatments. These results suggest nutrient availability may affect the biologically-mediated fate (new biomass vs respiration) of CDOC. 相似文献
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