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Highlighted publications of February 2015


Biophys J. 2015 Feb 17;108(4):863-71.

Histones cause aggregation and fusion of lipid vesicles containing phosphatidylinositol-4-phosphate.

Lete MG1, Sot J1, Gil D2, Valle M2, Medina M3, Goñi FM1, Alonso A4.

Source

1 Unidad de Biofísica (CSIC, UPV/EHU), Universidad del País Vasco, Leioa, Spain; Departamento de Bioquímica, Universidad del País Vasco, Leioa, Spain.
2 Structural Biology Unit, Center for Cooperative Research in Biosciences, CIC bioGUNE, Derio, Spain.
3 Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, Zaragoza, Spain; Instituto de Biocomputación y Física de Sistemas Complejos, Unidad Asociada BIFI-IQFR, Universidad de Zaragoza, Zaragoza, Spain.
4 Unidad de Biofísica (CSIC, UPV/EHU), Universidad del País Vasco, Leioa, Spain; Departamento de Bioquímica, Universidad del País Vasco, Leioa, Spain. Electronic address: alicia.alonso@ehu.es.

Abstract

In a previous article, we demonstrated that histones (H1 or histone octamers) interact with negatively charged bilayers and induce extensive aggregation of vesicles containing phosphatidylinositol-4-phosphate (PIP) and, to a lesser extent, vesicles containing phosphatidylinositol (PI). Here, we found that vesicles containing PIP, but not those containing PI, can undergo fusion induced by histones. Fusion was demonstrated through the observation of intervesicular mixing of total lipids and inner monolayer lipids, and by ultrastructural and confocal microscopy studies. Moreover, in both PI- and PIP-containing vesicles, histones caused permeabilization and release of vesicular aqueous contents, but the leakage mechanism was different (all-or-none for PI and graded release for PIP vesicles). These results indicate that histones could play a role in the remodeling of the nuclear envelope that takes place during the mitotic cycle.

PMID: 25692591



J Am Chem Soc. 2015 Feb 11;137(5):1850-61.

Pre-Gating Conformational Changes in the ChETA Variant of Channelrhodopsin-2 Monitored by Nanosecond IR Spectroscopy.

Lórenz-Fonfría VA, Schultz BJ, Resler T, Schlesinger R, Bamann C, Bamberg E, Heberle J.

Source

Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin , Arnimallee 14, 14195 Berlin, Germany.

Abstract

Light-gated ion permeation by channelrhodopsin-2 (ChR2) relies on the photoisomerization of the retinal chromophore and the subsequent photocycle, leading to the formation (on-gating) and decay (off-gating) of the conductive state. Here, we have analyzed the photocycle of a fast-cycling ChR2 variant (E123T mutation, also known as ChETA), by time-resolved UV/vis, step-scan FT-IR, and tunable quantum cascade laser IR spectroscopies with nanosecond resolution. Pre-gating conformational changes rise with a half-life of 200 ns, silent to UV/vis but detected by IR spectroscopy. They involve changes in the peptide backbone and in the H-bond of the side chain of the critical residue D156. Thus, the P1(500) intermediate must be separated into early and late states. Light-adapted ChR2 contains a mixture of all-trans and 13-cis retinal in a 70:30 ratio which are both photoactive. Analysis of ethylenic and fingerprint vibrations of retinal provides evidence that the 13-cis photocycle recovers in 1 ms. This recovery is faster than channel off-gating and most of the proton transfer reactions, implying that the 13-cis photocycle is of minor functional relevance for ChR2.

PMID: 25584873









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