16 research outputs found

    Analysis of PorACj purification.

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    <p>(A) Western blot analysis illustrating IMAC purification of his-tagged PorACj protein. The protein was expressed in <i>C. glutamicum</i> ATCC13032 <i>ΔporHΔporA</i> and purified by Ni<sup>2+</sup> affinity from the supernatant of detergent extracted whole cells. CMDIE represents chloroform-methanol treated cells in which the crude protein content was concentrated around 8 fold by diethyl-ether precipitation of pXJK0268His transfected (+) or non-transfected (−) <i>C. glutamicumΔporHΔporA</i> cells. Subsequent to tricine (12%)-SDS-PAGE the gel was blotted on a nitrocellulose membrane and PorACj-His was visualized by Anti-His antibodies and a chemiluminescent reaction. All samples were boiled for 5 minutes in Redmix before loading. (B) Silver stained tricine (16.5%)-SDS-PAGE of Ni<sup>2+</sup>-purified and factor Xa digested PorACj-His protein. Lanes: 1, 3 units of protease Xa (control); 2, 10 ”l of three pooled Ni-NTA elution containing PorACj-His; 3, 10 ”l of protease Xa treated and purified PorACj protein (for details see text). The dot blot immunoassay pictures underneath lanes 2 and 3 show cleavage of the histidine tail using anti-his antibody of 5 ”l of the corresponding protein samples. Before loading all samples were boiled for 5 minutes in Redmix.</p

    Analysis of secondary structure of PorACj usinf CD-spectrometry.

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    <p>A: CD spectra of recombinant PorACj (69 ”M) and PorA-His<sub>8</sub> (12 ”M) solubilized in 0.5% Genapol, 100 mM NaCl, 50 mM TrisHCl and 1 mM CaCl<sub>2</sub>, pH 8 measured at room temperature. B: CD-spectra of the same protein samples as in (A). The aqueous solutions of the proteins was supplemented with 4 M urea to destroy the secondary structure of the proteins.</p

    Dendrogram representing the phylogenetic relationships of PorA and PorH of different <i>Corynebacterium</i> species obtained by the neighbor-joining method.

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    <p>The tree was derived from the alignments of corresponding gene sequences. The support of each branch, as determined from 1,000 bootstrap samples, is indicated by the value at each node (in percent).The software used to construct alignment and tree was MEGA5.1.The sequence was aligned by ClustalW. Parameters: Multiple Alignment: Gap Opening Penalty: 10; Gap Extension Penalty: 0.2; Protein Weight Matrix: Gonnet; Gap Separation Distance: 4; Delay Divergent Cutoff (%): 30; The phylogenetic tree of corynebacterial species was constructed using the Maximum Likelihood statistical method; Substitution Model; Substitutions Type: Amino acid; Model/Method: Jones-Taylor-Thornton (JTT) model <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075651#pone.0075651-Tamura1" target="_blank">[81]</a>.</p

    Investigation of the voltage-dependence of PorACj in single-channel experiments.

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    <p>A: The purified protein was added to the <i>cis</i>-side of a PC membrane (10 ng/ml) and the reconstitution of channels was followed until about 10 PorACj-channels inserted into the membrane. Then 40 mV were applied to the <i>cis</i>-side of the membrane, and the membrane current was measured as a function of time. The aqueous phase contained 1M KCl; T = 20°C. B: Histogram of 56 closing events of the experiment in A and and similar experiments. The closing events were plotted in a bargraph as a function of the conductance of the closing events. ! M KCl; T = 20°C. Note that the PorACj channels closed in two distinct conductance values of 1 and 2 nS.</p

    Conductance (G) at a given membrane potential (V<sub>m</sub>) divided by the conductance at 10

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    <p> <b>mV (G<sub>0</sub>) expressed as a function of the membrane potential.</b> The symbols represent the mean (± SD) of six measurements, in which pure PorACj protein was added to the <i>cis</i>-side of the membranes. The aqueous phase contained 1 M KCl and 100 ng/ml porin. The membranes were formed from PC/<i>n</i>-decane at a temperature of 20°C.</p

    Analysis of the putative quaternary structure of PorACj.

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    <p>(A) Model of the octameric form of the PorACj channel in a lipid bilayer PorACj seen perpendicular to the membrane surface. Top view describes the initial setup of eight straight helices arranged in a circular manner to form a tube with a diameter of about 1.4 nm as derived from the experimental measurements. While the secondary structure is colored in purple, the individual amino-acid side chains are depicted as ball chains and colored according to their electrophysiological nature, i.e., neutral/hydrophobic in grey, polar in green, and charged in red (negative) and blue (positive), respectively. The surrounding bilayer is drawn as a grey surface. (B) Side view of the model of the octameric PorACj channel. After a few tenth of nanoseconds of unbiased molecular dynamics simulations, the helices kink in the central region - forming an hourglass shape - where several short side chains of the amino acids are located. The blue ball-stick side chains represent the lysines in the lower region, which are presumably responsible for the ion selectivity of PorACj and which form some kind of constriction zone.</p

    Radii of the anions and relative permeability of PorACj from <i>C. jeikeium</i> in different salt solutions.

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    <p>The data for the limiting conductivities of the different ions were taken from ref. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075651#pone.0075651-TonThat1" target="_blank">[66]</a>. The radii of the hydrated anions were calculated using the Stokes equation <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075651#pone.0075651-Trias3" target="_blank">[67]</a>. The single channel conductance of PorACj for the different salts at 0.1 M was taken from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075651#pone-0075651-t003" target="_blank">Table 3</a>. The relative permeability of the single anions was calculated by dividing the single-channel conductance of the individual anion by that of 0.1 M KBr. The relative permeability for 0.1 M KBr was set to unity.</p

    Study of pore-forming capacity of purified PorACj.

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    <p>(A) Single-channel recording of a PC/<i>n</i>-decane membrane in the presence of pure PorACj. The aqueous phase contained 1 M KCl, pH 6 and 10 ng/ml protein. The applied membrane potential was 20 mV; T = 20<sup>°</sup>C. (B) Histogram of the probability P(G) for the occurrence of a given conductivity unit observed with membranes formed of 1% PC dissolved in <i>n</i>-decane. It was calculated by dividing the number of fluctuations with a given conductance rise by the total number of conductance fluctuations in the presence of pure PorACj. Two frequent conductive units were observed for 295 single events taken from eight individual membranes. The average conductance of the steps corresponding to the left-side maximum was 1.25 nS and that of the right-side maximum was 2.5 nS. The aqueous phase contained 1 M KCl, pH 6 and 10 ng/ml protein, the applied membrane potential was 20 mV, T = 20°C.</p

    Fit of the single-channel conductance data of PorACj by using the Renkin correction factor times the aqueous diffusion coefficients of the different anions

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    <p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075651#pone.0075651-Trias3" target="_blank">[<b>67</b>]</a><b>.</b> The product of both numbers was normalized to 1 for a = 1.05 nm (Br<sup>−</sup>). Single-channel conductance was normalized to the one of 0.1 M KBr and plotted versus the hydrated ion radii taken from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075651#pone-0075651-t003" target="_blank">Table 3</a>. The single-channel conductance correspond to Br<sup>−</sup>, Cl<sup>−</sup>, NO<sub>3</sub><sup>−</sup>, ClO<sub>3</sub><sup>−</sup>, F<sup>−</sup>, HCOO<sup>−</sup> and CH<sub>3</sub>COO<sup>−</sup> which were all used for the pore diameter estimation. The fit (solid lines) is shown for r = 0.5 nm (lower line) and r = 0.9 nm (upper line). The best fit was achieved with r = 0.7 nm (diameter = 1.4 nm) corresponding to the broken line.</p
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