1,721,151 research outputs found
The interactions of retinol carriers with model membranes provide insights into the complex mechanisms of ligand binding and release
No full textThe Center for International Cooperation and the Master in International Health of Parma University
No full textWhat do we learn by comparing the solution and crystal structures of two members of the calycin protein superfamily ?
No full textProbing the positioning of CRBPs upon phospholipid bilayers interaction by a suite of NMR experiments
No full textVitamin A must be adequately distributed within the mammalian body to produce visual chromophore in the eyes and all-trans-retinoic acid in other tissues. The cellular trafficking and metabolism of vitamin A are regulated primarily by specific high-affinity carriers called CRBP-I and CRBP-II. Both proteins deliver retinol to microsomal membrane-bound enzymes, either for esterification with fatty acids (LRAT) [1, 2] or for oxidation to retinaldehyde (RDH) [3]. Our current understanding of these processes remains incomplete, but there is evidence that the membrane microenvironment plays a role in the interactions of holo CRBPs with enzymes [3].
To address this hypothesis, we have performed a suite of NMR experiments with retinol-bound CRBP-I and CRBP-II in the presence of model membranes composed of either anionic or zwitterionic phospholipids, at varying protein:lipid molar ratios and ionic strength. Besides NMR, other biophysical techniques were employed to achieve a better understanding of the ongoing processes.
TROSY spectra provided insights into the involved protein residues and conformational dynamics. The interaction with the liposomes differs significantly between the two homologous proteins; moreover, it depends upon the phospholipid charge and ionic strength, suggesting an electrostatic nature of the binding.
The data indicate that holo CRBP-I, in contrast to CRBP-II, interacts more strongly with the anionic lipid vesicles and some conformational changes are observed in the ligand entry portal. Nevertheless, there is apparently no protein region embedded inside the bilayer, as judged by H/D exchange measurements.
This study may help to understand certain aspects of the mechanisms of ligand delivery by CRBPs.
References
[1] J. Amengual, M. Golczak, K. Palczewski, and J.von Lintig J. Biol. Chem. 287, 24216-24227 (2012).
[2] W. Jiang and J.L. Napoli Biochim. Biophys. Acta 1820, 859-869 (2012).
[3] J.L. Napoli Biochim. Biophys. Acta 1821, 152-167 (2012)
Steady-State and Time Resolved Characterization of a New Fluorescent Phospholipid to Study the Excited-State Proton Transfer Processes at the Membrane Surface
No full textSemi-automatic Stereospecific Resonance and NOESY Assignment of Proteins Based on the Tertiary Structure – the Program nmr2st
No full textThe collaboration of the University Center for International Cooperation with the Geneva Foundation for Medical Education and Research in training health professionals
No full textStereospecific assignments of protein NMR resonances based on the tertiary structure and 2D/3D NOE data
No full textIn many cases of protein structure determination by NMR a high-quality structure is required. An important
contribution to structural precision is stereospecific assignment of magnetically nonequivalent prochiral methylene and
methyl groups, eliminating the need for introducing pseudoatoms and pseudoatom corrections in distance restraint lists.
Here, we introduce the stereospecific assignment program that uses the resonance assignment, a preliminary 3D structure
and 2D and/or 3D nuclear Overhauser effect spectroscopy peak lists for stereospecific assignment. For each prochiral
group the algorithm automatically calculates a score for the two different stereospecific assignment possibilities, taking
into account the presence and intensity of the nuclear Overhauser effect (NOE) peaks that are expected from the local
environment of each prochiral group (i.e., the close neighbors). The performance of the algorithm has been tested and
used on NMR data of -helical and -sheet proteins using homology models and/or X-ray structures. The program
produced no erroneus stereospecific assignments provided the NOEs were carefully picked and the 3D model was
sufficiently accurate. The set of NOE distance restraints produced by nmr2st using the results of the SSA module was
superior in generating good-quality ensembles of NMR structures (low deviations from upper limits in conjunction with
low root-mean-square-deviation values) in the first round of structure calculations. The program uses a novel approach
that employs the entire 3D structure of the protein to obtain stereospecific assignment; it can be used to speed up the
NMR structure refinement and to increase the quality of the final NMR ensemble even when no scalar or residual dipolar
coupling information is available
2-Naphthol-Phosphatidylethanolamine: A Fluorescent Phospholipid Analogue for Excited-State Proton Transfer Studies in Membranes
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