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Interactions of archaeal chromatin proteins Alba1 and Alba2 with nucleic acids.

Črnigoj M, Podlesek Z, Zorko M, Jerala R, Anderluh G, Ulrih NP - PLoS ONE (2013)

Bottom Line: Alba2 and equimolar mixtures of Alba1/Alba2 have greater effects on the thermal stability of poly(dA-dT).poly(dA-dT).The secondary structures of the Alba proteins are not significantly influenced by DNA binding, even at high temperatures.Based on these data, we conclude that Alba1, Alba2, and equimolar mixtures of Alba1/Alba2 show different properties in their binding to various DNAs.

View Article: PubMed Central - PubMed

Affiliation: Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.

ABSTRACT

Background: Architectural proteins have important roles in compacting and organising chromosomal DNA. There are two potential histone counterpart peptide sequences (Alba1 and Alba2) in the Aeropyrum pernix genome (APE1832.1 and APE1823).

Methodology/principal findings: THESE TWO PEPTIDES WERE EXPRESSED AND THEIR INTERACTIONS WITH VARIOUS DNAS WERE STUDIED USING A COMBINATION OF VARIOUS EXPERIMENTAL TECHNIQUES: surface plasmon resonance, UV spectrophotometry, circular dichroism-spectropolarimetry, gel-shift assays, and isothermal titration calorimetry.

Conclusions/significance: Our data indicate that there are significant differences in the properties of the Alba1 and Alba2 proteins. Both of these Alba proteins can thermally stabilise DNA polynucleotides, as seen from UV melting curves. Alba2 and equimolar mixtures of Alba1/Alba2 have greater effects on the thermal stability of poly(dA-dT).poly(dA-dT). Surface plasmon resonance sensorgrams for binding of Alba1, Alba2, and equimolar mixtures of Alba1/Alba2 to DNA oligonucleotides show different binding patterns. Circular dichroism indicates that Alba2 has a less-ordered secondary structure than Alba1. The secondary structures of the Alba proteins are not significantly influenced by DNA binding, even at high temperatures. Based on these data, we conclude that Alba1, Alba2, and equimolar mixtures of Alba1/Alba2 show different properties in their binding to various DNAs.

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CD spectra of Alba1/Alba2 complex.Molar ellipticity, [Θ], in the far-UV range (200–250 nm) at different temperatures (as indicated), for the Alba1/Alba2 complex without bound DNA (a), with CT-DNA (b), with AT-DNA (c), and with GC-DNA (d). Molar ratio of Alba:DNA per base pair was 1∶5 at pH 7.0 (50 mM NaH2PO4).
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pone-0058237-g009: CD spectra of Alba1/Alba2 complex.Molar ellipticity, [Θ], in the far-UV range (200–250 nm) at different temperatures (as indicated), for the Alba1/Alba2 complex without bound DNA (a), with CT-DNA (b), with AT-DNA (c), and with GC-DNA (d). Molar ratio of Alba:DNA per base pair was 1∶5 at pH 7.0 (50 mM NaH2PO4).

Mentions: The Alba1/Alba2 complex preserved its secondary structure content as the temperature was raised from 25°C to 70°C (25% α-helices, 48% β-sheet and 27% β-turns). As the temperature increased further, to 90°C, the amount of β-sheet increased to 61% at the expense of a decrease in the β-turn content, to 10% (Figure 9a). In the presence of CT-DNA, the equimolar mixture of Alba1/Alba2 underwent a slight change in secondary structure. As for each Alba protein measured separately, in the equimolar mixture Alba1/Alba2, a more ordered structure was gained at higher temperatures (with the most apparent increase seen in the β-sheet content). In the presence of AT-DNA and GC-DNA, Alba1/Alba2 did not trigger any significant changes in the conformation of the proteins (at 25°C), with the amount of β-sheet increasing with the increase in temperature (Figure 9 c, d).


Interactions of archaeal chromatin proteins Alba1 and Alba2 with nucleic acids.

Črnigoj M, Podlesek Z, Zorko M, Jerala R, Anderluh G, Ulrih NP - PLoS ONE (2013)

CD spectra of Alba1/Alba2 complex.Molar ellipticity, [Θ], in the far-UV range (200–250 nm) at different temperatures (as indicated), for the Alba1/Alba2 complex without bound DNA (a), with CT-DNA (b), with AT-DNA (c), and with GC-DNA (d). Molar ratio of Alba:DNA per base pair was 1∶5 at pH 7.0 (50 mM NaH2PO4).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3585288&req=5

pone-0058237-g009: CD spectra of Alba1/Alba2 complex.Molar ellipticity, [Θ], in the far-UV range (200–250 nm) at different temperatures (as indicated), for the Alba1/Alba2 complex without bound DNA (a), with CT-DNA (b), with AT-DNA (c), and with GC-DNA (d). Molar ratio of Alba:DNA per base pair was 1∶5 at pH 7.0 (50 mM NaH2PO4).
Mentions: The Alba1/Alba2 complex preserved its secondary structure content as the temperature was raised from 25°C to 70°C (25% α-helices, 48% β-sheet and 27% β-turns). As the temperature increased further, to 90°C, the amount of β-sheet increased to 61% at the expense of a decrease in the β-turn content, to 10% (Figure 9a). In the presence of CT-DNA, the equimolar mixture of Alba1/Alba2 underwent a slight change in secondary structure. As for each Alba protein measured separately, in the equimolar mixture Alba1/Alba2, a more ordered structure was gained at higher temperatures (with the most apparent increase seen in the β-sheet content). In the presence of AT-DNA and GC-DNA, Alba1/Alba2 did not trigger any significant changes in the conformation of the proteins (at 25°C), with the amount of β-sheet increasing with the increase in temperature (Figure 9 c, d).

Bottom Line: Alba2 and equimolar mixtures of Alba1/Alba2 have greater effects on the thermal stability of poly(dA-dT).poly(dA-dT).The secondary structures of the Alba proteins are not significantly influenced by DNA binding, even at high temperatures.Based on these data, we conclude that Alba1, Alba2, and equimolar mixtures of Alba1/Alba2 show different properties in their binding to various DNAs.

View Article: PubMed Central - PubMed

Affiliation: Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.

ABSTRACT

Background: Architectural proteins have important roles in compacting and organising chromosomal DNA. There are two potential histone counterpart peptide sequences (Alba1 and Alba2) in the Aeropyrum pernix genome (APE1832.1 and APE1823).

Methodology/principal findings: THESE TWO PEPTIDES WERE EXPRESSED AND THEIR INTERACTIONS WITH VARIOUS DNAS WERE STUDIED USING A COMBINATION OF VARIOUS EXPERIMENTAL TECHNIQUES: surface plasmon resonance, UV spectrophotometry, circular dichroism-spectropolarimetry, gel-shift assays, and isothermal titration calorimetry.

Conclusions/significance: Our data indicate that there are significant differences in the properties of the Alba1 and Alba2 proteins. Both of these Alba proteins can thermally stabilise DNA polynucleotides, as seen from UV melting curves. Alba2 and equimolar mixtures of Alba1/Alba2 have greater effects on the thermal stability of poly(dA-dT).poly(dA-dT). Surface plasmon resonance sensorgrams for binding of Alba1, Alba2, and equimolar mixtures of Alba1/Alba2 to DNA oligonucleotides show different binding patterns. Circular dichroism indicates that Alba2 has a less-ordered secondary structure than Alba1. The secondary structures of the Alba proteins are not significantly influenced by DNA binding, even at high temperatures. Based on these data, we conclude that Alba1, Alba2, and equimolar mixtures of Alba1/Alba2 show different properties in their binding to various DNAs.

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