Structure and orientation of two voltage-dependent anion-selective channel isoforms. An attenuated total reflection fourier-transform infrared spectroscopy study.
Two VDAC (voltage-dependent anion-selective channel) isoforms were purified from seed cotyledons of Phaseolus vulgaris by chromatofocusing chromatography. Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy was used to study the structural properties of the two isoforms reconstituted in a mixture of asolectin and 5% stigmasterol. The IR spectra of the two VDAC isoforms were highly similar indicating 50 to 53% anti-parallel beta-sheet. The orientation of the beta-strands relative to the barrel axis was calculated from the experimentally obtained dichroic ratios of the amide I beta-sheet component and the amide II band. Comparing the IR spectra of the reconstituted VDAC isoforms with the IR spectra of the bacterial porin OmpF, for which a high resolution structure is available, provided evidence for a general structural organization of the VDAC isoforms similar to that of bacterial porins. Hydrogen-deuterium exchange measurements indicated that the exchange of the amide protons occurs to a higher extent in the two VDAC isoforms than in the OmpF porin.
Abrecht
H
H
Laboratoire de Physiologie Végétale, CP 206/2, Faculté des Sciences, Université Libre de Bruxelles, Bld du Triomphe, B-1050 Brussels, Belgium.
Goormaghtigh
E
E
Ruysschaert
J M
JM
Homble
F
F
D003903:Deuterium; D006860:Hydrogen Bonding; D007473:Ion Channels / Q000737:chemistry*; D018272:Porins / Q000737:chemistry* / Q000302:isolation & purification; D020033:Protein Isoforms / Q000737:chemistry; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D050994:Voltage-Dependent Anion Channels
D007473:Ion Channels; D018272:Porins; D020033:Protein Isoforms; D050994:Voltage-Dependent Anion Channels; D003903:Deuterium