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Wiechlina roczna (Poa annua) - gatunek inwazyjny we florze naczyniowej Antarktyki.
Get PDFLądowy ekosystem Antarktyki cechuje
skrajne ubóstwo gatunkowe. Dotyczy to
przede wszystkim roślin kwiatowych reprezentowanych
jedynie przez dwa rodzime gatunki.
Są nimi: trawa — śmiałek antarktyczny
(Deschampsia antarctica Desv.) z rodziny
Poaceae i Colobanthus quitensis — przedstawiciel
rodziny goździkowatych (Caryophyllaceae).
W wolnych od lodu rejonach Antarktyki
rozwija się uboga tundra złożona prawie
wyłącznie z organizmów zarodnikowych.
Dominującą grupę stanowią porosty, których
bogactwo w Antarktyce szacowane jest na
przeszło 400 gatunków (Olech 2001, 2004;
Øvstedal i Lewis Smith 2001; Olech i Singh
2009), ale wciąż opisywane są nowe dla nauki
gatunki (Olech i Bystrek 2004, Olech
i Czarnota 2009, Osyczka i Olech 2011).
Znaczną rolę w budowie tundry antarktycznej
odgrywają także mchy, których lista obejmuje
111 gatunków (Ochyra i współaut.
2008).
Struktura i skład florystyczny zbiorowisk
tundry zależy od stabilności podłoża,
dostępności wody i zawartości substancji
biogennych (Olech 2002). Na suchych, zajmujących
duże powierzchnie siedliskach,
zwłaszcza tych położonych w głębi lądu,
rozwijają się przede wszystkim zbiorowiskaporostów. W miejscach wilgotnych, czasem
ze stagnującą wodą, występują higrofilne
zbiorowiska mszyste. W niższych partiach
terenu, Antarktyki morskiej, zwłaszcza na
równinach nadmorskich, gdzie panują bardziej
dogodne warunki siedliskowe, spotyka
się zbiorowiska z dominacją roślin kwiatowych,
śmiałka antarktycznego i kolobanta.
Towarzyszą im zwykle mchy, a w pobliżu
kolonii ptaków, także nitrofilne glony i
sinice.
Jednym z czynników decydujących o
specyfice ekosystemów antarktycznych jest
izolacja tego obszaru spowodowana atmosferyczną
i morską cyrkulacją. Tylko dwa gatunki
roślin kwiatowych, spośród kilkuset
występujących na Ziemi Ognistej (Ameryka
Południowa), zdołały przekroczyć Cieśninę
Drake’a i zasiedliły rejony morskiej Antarktyki.
Lista gatunków tego najuboższego florystycznie
regionu kuli ziemskiej powiększyła
się ostatnio o trzeci gatunek rośliny
kwiatowej, Poa annua L., która początkowo
opanowała siedliska antropogeniczne,
a obecnie siedliska naturalne w miejscach
niedawno uwolnionych spod lodu, gdzie
wchodzi w skład zbiorowisk tundrowych
CpG underrepresentation and the bacterial CpG-specific DNA methyltransferase M.MpeI
Get PDFCytosine methylation promotes deamination. In eukaryotes, CpG methylation is thought to account for CpG underrepresentation. Whether scarcity of CpGs in prokaryotic genomes is diagnostic for methylation is not clear. Here, we report that Mycoplasms tend to be CpG depleted and to harbor a family of constitutively expressed or phase variable CpG-specific DNA methyltransferases. The very CpG poor Mycoplasma penetrans and its constitutively active CpG-specific methyltransferase M.MpeI were chosen for further characterization. Genome-wide sequencing of bisulfite-converted DNA indicated that M.MpeI methylated CpG target sites both in vivo and in vitro in a locus-nonselective manner. A crystal structure of M.MpeI with DNA at 2.15-Å resolution showed that the substrate base was flipped and that its place in the DNA stack was taken by a glutamine residue. A phenylalanine residue was intercalated into the "weak" CpG step of the nonsubstrate strand, indicating mechanistic similarities in the recognition of the short CpG target sequence by prokaryotic and eukaryotic DNA methyltransferases
Isolation of monomeric photosystem II that retains the subunit PsbS
Get PDFPhotosystem II has been purified from a transplastomic strain of Nicotiana tabacum according to two different protocols. Using the procedure described in Piano et al. (Photosynth Res 106:221-226, 2010) it was possible to isolate highly active PSII composed of monomers and dimers but depleted in their PsbS protein content. A "milder" procedure than the protocol reported by Fey et al. (Biochim Biophys Acta 1777:1501-1509, 2008) led to almost exclusively monomeric PSII complexes which in part still bind the PsbS protein. This finding might support a role for PSII monomers in higher plants
Altering the fungal cell wall integrity and practical aspects of these modifications
Get PDFIn this chapter we compare the cell wall structure of filamentous fungi and the yeast Saccharomyces cerevisiae. The genetic engineering of the cell wall of Trichoderma, Aspergillus, Neurospora, S. cerevisiae, Schizosaccharomyces pombe, Hansenula polymorpha, Kluyveromyces and others is discussed and the consequences of direct changes in the synthesis of cell wall components, especially those affecting protein production and secretion by the mutants and their sensitivity to antifungal agents are highlighted. Furthermore, we discuss the close correlation between the cell wall structure and the activity of enzymes engaged in protein glycosylation and in the biosynthesis of glycosylphosphatidylinositol anchors.
We also show problems with stability of the generated changes in the cell wall structure, which are detected and often overcome by cell wall compensatory mechanisms
Impact of calcium binding and thionylation of S100A1 protein on its NMR derived structure and backbone dynamics
No full textS100 proteins play a crucial role in multiple important biological processes in vertebrate organisms acting predominantly as calcium signal transmitters. S100A1 is a typical representative of this family of proteins. Upon binding of four Ca2+ ions it undergoes a dramatic conformational change, resulting in exposure, in each of its two identical subunits, a large hydrophobic cleft that binds to target proteins. It has been shown that abnormal expression of S100A1 is strongly correlated with a number of severe human diseases: cardiomyopathy and neurodegenerative disorders.
A few years ago we have found that thionylation of Cys 85 - the unique cysteine in two identical S100A1 subunits – leads to a drastic increase of the protein affinity for calcium. We postulated that the protein activated by thionylation becomes a more efficient calcium signal transmitter. Therefore, we decided to undertake, using NMR methods, a comparative study of structure and dynamics of native and thionylated human S100A1 in its apo and holo states. In this paper we present the results obtained for the both forms of this protein in its holo state and compare them with the previously published structure of native apo S100.
The main conclusion that we draw from these results is that the increased calcium binding affinity of S100A1 upon thionylation arises, most probably, from rearrangement of the hydrophobic core in its apo form
Active Stable Maintenance Functions in Low Copy-Number Plasmids of Gram-positive Bacteria II. Post-segregational Killing Systems
Get PDFActive support is needed for low copy-number plasmids to be stably maintained in bacterial cells. !e mechanisms that fulfill this role are (i) partition systems (PAR) acting to separate plasmid molecules to daughter cells and (ii) toxin-andidote (TA) (post-segregational killing-PSK) systems which arrest cell growth until the plasmid reaches the correct copy-number or kill the cells that have not inherited the plasmid. Our knowledge of toxin-antidote systems comes mainly from studies on Gram-negative bacteria. However, some addiction systems of Gram-positive bacteria have been characterized in detail or recently identified. Altogether, they bring new interesting data on toxin-antidote functioning in bacteria
Direct targeting of Arabidopsis cysteine synthase complexes with synthetic polypeptides to selectively deregulate cysteine synthesis
Get PDFBiosynthesis of cysteine is one of the fundamental processes in plants providing the reduced sulfur for
cell metabolism. It is accomplished by the sequential action of two enzymes, serine acetyltransferase
(SAT) and O-acetylserine (thiol) lyase (OAS-TL). Together they constitute the hetero-oligomeric cysteine
synthase (CS) complex through specific protein–protein interactions influencing the rate of cysteine
production. The aim of our studies was to deregulate the CS complex formation in order to investigate its
function in the control of sulfur homeostasis and optimize cysteine synthesis. Computational modeling
was used to build a model of the Arabidopsis thaliana mitochondrial CS complex. Several polypeptides
based on OAS-TL C amino-acid sequence found at SAT-OASTL interaction sites were designed as probable
competitors for SAT3 binding. After verification of the binding in a yeast two-hybrid assay, the most
strongly interacting polypeptide was introduced to different cellular compartments of Arabidopsis cell via
genetic transformation. Moderate increase in total SAT and OAS-TL activities, but not thiols content, was
observed dependent on the transgenic line and sulfur availability in the hydroponic medium. Though our
studies demonstrate the proof of principle, they also suggest more complex interaction of both enzymes
underlying the mechanism of their reciprocal regulation
Towards a novel influenza vaccine: engineering of hemagglutinin on a platform of adenovirus dodecahedron
Get PDFBackground: The production process for the current influenza vaccine takes about 6 months and its antigenic
composition must be modified annually. In the attempt towards developing influenza vaccine production that
would be faster, safer and cheaper we engineered an influenza vaccine in which multiple copies of hemagglutinin
(HA) would be delivered by a vector, adenovirus dodecahedron (Ad Dd). Dd is a virus-like particle, formed by
assembly of twelve copies of pentameric penton base (Pb) proteins responsible for virus penetration. In order to
attach HA to the vector, an adaptor containing WW domains was used. The WW domain is a linear peptide
fragment identified as a partner of proline-proline-x-tyrosine (PPxY) motif present at the N-terminal extremity of the
Pb protein, which is a building block of Dd. That tandem of three WW domains in fusion with the protein of
interest enables interaction with Dd and efficient translocation to the cytoplasm of cells in culture.
Results: Since HA is an oligomeric protein with complicated processing, we prepared six different constructs of HA
(A/swan/Poland/467/2006(H5N1)) in fusion with the WW adaptor. Herein we report baculovirus expression and functional analysis of six HA-WW variants. The best behaving variant was successfully delivered into human cells in vitro.
Conclusions: Engineering of a soluble complex of HA with Dd, a virus-like particle that serves as a vector, an adjuvantand as a multivalent presentation platform, is an important step toward a novel influenza vaccine.
Keywords: Influenza vaccine, Hemagglutinin, Adenovirus dodecahedron, WW-domain adaptor, Vaccine presentation platform, Multivalenc
Non-specific clustering of histidine tagged green fluorescent protein mediated by surface interactions: the collective effect in the protein-adsorption behaviour
Get PDFThe chemically programmed non-fouling surfaces were used to observe the surface assembly behaviour of hexahistidine tagged Green Fluorescent Protein (His-GFP) as a model protein. In this particular case, site-selective physisorption of His-GFP was achieved in the absence of metal ions. This preference does not arise from surface charge, wettability or topographic differences between regions. We found that His-GFP has a tendency to centre into an array of marked squares and acquires a template shape on the entire non-fouling surface when both the internal and surrounding areas present carboxylate groups. This surface-directed organization of protein in assemblies is an unusual example of non-specific molecular interactions transfer to a higher scale objects organization. Furthermore, we performed a proof-of-concept study for the autonomous formation of protein microarrays with uniform orientation of the tagged protein molecules on the surface. Periodic protein microarrays were formed spontaneously within about one minute after the deposition of a few drops of protein solutions on the substrate. We propose a simple, gentle and cost-effective approach to fabrication of protein microarrays, which can be done by the end-user. This phenomenon of collective protein clustering into large scale patterns may help to assess experimentally how the peripheral proteins arrange into separate domains of the cell membrane
Zmiany w populacjach ptaków i ssaków płetwonogich Antarktyki Zachodniej
Get PDFThe Southern Ocean marine ecosystem has been
exploited commercially for over 200 years. Selective
harvesting of various components of the food web
led to significant changes in the structure of this
ecosystem. Recently, these negative changes are exacerbated
by increased tourist traffic and expanding
infrastructure of Antarctic stations. Moreover, currently
observed rapid environmental changes, expressed
in changing temperature, wind and precipitation,
may potentially lead to major environmental
perturbations in this very sensitive region. Among
the major effects of the atmospheric warming are
changes within the sea-ice cover, which affects not
only abundance of krill, the main food base of Antarctic
marine predators, but also nesting and breeding
areas available for penguins. Therefore, the environmental
changes pose a new challenge to the
survival of Antarctic wildlife. Study of the complex
interactions between the animals life cycles, abundance
of food, and predators pressure imposed by
birds and pinnipeds, explain some trends in the
populations dynamics. Bird and pinniped species
and their response to the climate perturbations, including
significant alternations of populations sizes
and changes of breading areas as well as changes in
arrival and laying dates, have been recorded as important
bio-indicators of changes in the Antarctic
ecosystem