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Membrane protein dynamics: limited lipid control.

Szalontai B - PMC Biophys (2009)

Bottom Line: In dissolved lysozyme, as a function of temperature, H/D exchange involved only reversible movements (the secondary structure did not change considerably); heat-denaturing was a separate event at much higher temperature.When temperature was further increased, H/D exchange rates went over a maximum and afterwards decreased (due to full H/D exchange and/or protein denaturing).Maximal H/D exchange rate temperatures correlated neither with the disorder nor with the unsaturation of lipids.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Biophysics, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, Temesvári krt, 62, P,O,B, 521, Hungary. balazs@brc.hu.

ABSTRACT
Correlation of lipid disorder with membrane protein dynamics has been studied with infrared spectroscopy, by combining data characterizing lipid phase, protein structure and, via hydrogen-deuterium (H/D) exchange, protein dynamics. The key element was a new measuring scheme, by which the combined effects of time and temperature on the H/D exchange could be separated. Cyanobacterial and plant thylakoid membranes, mammalian mitochondria membranes, and for comparison, lysozyme were investigated. In dissolved lysozyme, as a function of temperature, H/D exchange involved only reversible movements (the secondary structure did not change considerably); heat-denaturing was a separate event at much higher temperature. Around the low-temperature functioning limit of the biomembranes, lipids affected protein dynamics since changes in fatty acyl chain disorders and H/D exchange exhibited certain correlation. H/D exchange remained low in all membranes over physiological temperatures. Around the high-temperature functioning limit of the membranes, the exchange rates became higher. When temperature was further increased, H/D exchange rates went over a maximum and afterwards decreased (due to full H/D exchange and/or protein denaturing). Maximal H/D exchange rate temperatures correlated neither with the disorder nor with the unsaturation of lipids. In membrane proteins, in contrast to lysozyme, the onsets of sizable H/D exchange rates were the onsets of irreversible denaturing as well. Seemingly, at temperatures where protein self-dynamics allows large-scale H/D exchange, lipid-protein coupling is so weak that proteins prefer aggregating to limit the exposure of their hydrophobic surface regions to water. In all membranes studied, dynamics seemed to be governed by lipids around the low-temperature limit, and by proteins around the high-temperature limit of membrane functionality.PACS codes: 87.14.ep, 87.14.cc, 87.16.D.

No MeSH data available.


Related in: MedlinePlus

Difference spectra for tobacco thylakoid membranes obtained by calculating D(i) = S(i+1) – S(i) from the series of measured S(i) spectra. Continuous blue curves indicate ISO difference spectra, where the temperature of the two spectra from which these difference spectra were calculated was the same. Red dash-dot curves indicate ΔT difference spectra, where there was about 3°C difference between the spectra from which these difference spectra were calculated. Arrows show the directions of the changes at the given spectrum region upon increasing temperature. Thicker lines show the different minima of the disappearing amide II band in the ISO and the ΔT spectra. The difference spectra of the studied temperature range (6–73°C) are divided into four panels according to their tendencies to change. The intensity scaling in the four panels is the same.
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Figure 2: Difference spectra for tobacco thylakoid membranes obtained by calculating D(i) = S(i+1) – S(i) from the series of measured S(i) spectra. Continuous blue curves indicate ISO difference spectra, where the temperature of the two spectra from which these difference spectra were calculated was the same. Red dash-dot curves indicate ΔT difference spectra, where there was about 3°C difference between the spectra from which these difference spectra were calculated. Arrows show the directions of the changes at the given spectrum region upon increasing temperature. Thicker lines show the different minima of the disappearing amide II band in the ISO and the ΔT spectra. The difference spectra of the studied temperature range (6–73°C) are divided into four panels according to their tendencies to change. The intensity scaling in the four panels is the same.

Mentions: The series of isotherm (ISO) and temperature difference (ΔT) difference spectra are shown in Figure 2. The spectra are grouped into four temperature ranges according to their characteristic features.


Membrane protein dynamics: limited lipid control.

Szalontai B - PMC Biophys (2009)

Difference spectra for tobacco thylakoid membranes obtained by calculating D(i) = S(i+1) – S(i) from the series of measured S(i) spectra. Continuous blue curves indicate ISO difference spectra, where the temperature of the two spectra from which these difference spectra were calculated was the same. Red dash-dot curves indicate ΔT difference spectra, where there was about 3°C difference between the spectra from which these difference spectra were calculated. Arrows show the directions of the changes at the given spectrum region upon increasing temperature. Thicker lines show the different minima of the disappearing amide II band in the ISO and the ΔT spectra. The difference spectra of the studied temperature range (6–73°C) are divided into four panels according to their tendencies to change. The intensity scaling in the four panels is the same.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2666629&req=5

Figure 2: Difference spectra for tobacco thylakoid membranes obtained by calculating D(i) = S(i+1) – S(i) from the series of measured S(i) spectra. Continuous blue curves indicate ISO difference spectra, where the temperature of the two spectra from which these difference spectra were calculated was the same. Red dash-dot curves indicate ΔT difference spectra, where there was about 3°C difference between the spectra from which these difference spectra were calculated. Arrows show the directions of the changes at the given spectrum region upon increasing temperature. Thicker lines show the different minima of the disappearing amide II band in the ISO and the ΔT spectra. The difference spectra of the studied temperature range (6–73°C) are divided into four panels according to their tendencies to change. The intensity scaling in the four panels is the same.
Mentions: The series of isotherm (ISO) and temperature difference (ΔT) difference spectra are shown in Figure 2. The spectra are grouped into four temperature ranges according to their characteristic features.

Bottom Line: In dissolved lysozyme, as a function of temperature, H/D exchange involved only reversible movements (the secondary structure did not change considerably); heat-denaturing was a separate event at much higher temperature.When temperature was further increased, H/D exchange rates went over a maximum and afterwards decreased (due to full H/D exchange and/or protein denaturing).Maximal H/D exchange rate temperatures correlated neither with the disorder nor with the unsaturation of lipids.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Biophysics, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, Temesvári krt, 62, P,O,B, 521, Hungary. balazs@brc.hu.

ABSTRACT
Correlation of lipid disorder with membrane protein dynamics has been studied with infrared spectroscopy, by combining data characterizing lipid phase, protein structure and, via hydrogen-deuterium (H/D) exchange, protein dynamics. The key element was a new measuring scheme, by which the combined effects of time and temperature on the H/D exchange could be separated. Cyanobacterial and plant thylakoid membranes, mammalian mitochondria membranes, and for comparison, lysozyme were investigated. In dissolved lysozyme, as a function of temperature, H/D exchange involved only reversible movements (the secondary structure did not change considerably); heat-denaturing was a separate event at much higher temperature. Around the low-temperature functioning limit of the biomembranes, lipids affected protein dynamics since changes in fatty acyl chain disorders and H/D exchange exhibited certain correlation. H/D exchange remained low in all membranes over physiological temperatures. Around the high-temperature functioning limit of the membranes, the exchange rates became higher. When temperature was further increased, H/D exchange rates went over a maximum and afterwards decreased (due to full H/D exchange and/or protein denaturing). Maximal H/D exchange rate temperatures correlated neither with the disorder nor with the unsaturation of lipids. In membrane proteins, in contrast to lysozyme, the onsets of sizable H/D exchange rates were the onsets of irreversible denaturing as well. Seemingly, at temperatures where protein self-dynamics allows large-scale H/D exchange, lipid-protein coupling is so weak that proteins prefer aggregating to limit the exposure of their hydrophobic surface regions to water. In all membranes studied, dynamics seemed to be governed by lipids around the low-temperature limit, and by proteins around the high-temperature limit of membrane functionality.PACS codes: 87.14.ep, 87.14.cc, 87.16.D.

No MeSH data available.


Related in: MedlinePlus