Lateral self-assembly of 18.5-kDa myelin basic protein (MBP) charge component-C1 on membranes.
Myelin basic protein (MBP), particularly the classic 18.5-kDa isoform, is a major structural protein of the myelin sheath of the central nervous system. It is an intrinsically disordered, peripheral membrane protein that shows structural polymorphism in combination with several overlapping interaction sites. Here, double electron-electron resonance (DEER) spectroscopy, in combination with a simplified, semi-quantitative analysis based on Monte Carlo simulations, is used to determine the distance distribution of murine 18.5-kDa MBP, unmodified charge component-C1, on large unilamellar vesicles of a lipid composition mimicking the cytoplasmic leaflet of myelin. Three singly spin-labeled MBP variants and a mixture of singly-labeled MBP variants are used. The MBPs, each bearing only one spin label, exhibit average intermolecular distances that are significantly shorter than the distances expected when assuming a random distribution at the employed lipid-to-protein ratios, indicating self-assembly on the membrane. The distribution of elliptical pervaded areas (hard ellipses) on a two-dimensional surface can serve as a model of the nonspecific self-assembly process. The corresponding pair correlation functions g(r) are determined from Monte Carlo simulations with variation of various parameters such as the ellipses' aspect ratios. Comparing the g(r) values with the DEER-derived distance distributions, the pervaded volume is best characterized by a nearly elliptical projection onto the membrane, with an aspect ratio of approximately 1.5, and with the longer semi-axis of approximately 1.4nm. The approach of using local information from DEER with low-resolution models derived from Monte Carlo simulations can be applied to study the lateral self-assembly properties of other protein complexes on membranes.
Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
Daniel R
DR
Kattnig
Timo
T
Bund
Joan M
JM
Boggs
George
G
Harauz
Dariush
D
Hinderberger
D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D009010:Monte Carlo Method; D004676:Myelin Basic Protein / Q000737:chemistry*
D004676:Myelin Basic Protein