Induced secondary structure and polymorphism in an intrinsically disordered structural linker of the CNS: solid-state NMR and FTIR spectroscopy of myelin basic protein bound to actin.
The 18.5 kDa isoform of myelin basic protein (MBP) is a peripheral membrane protein that maintains the structural integrity of the myelin sheath of the central nervous system by conjoining the cytoplasmic leaflets of oligodendrocytes and by linking the myelin membrane to the underlying cytoskeleton whose assembly it strongly promotes. It is a multifunctional, intrinsically disordered protein that behaves primarily as a structural stabilizer, but with elements of a transient or induced secondary structure that represent binding sites for calmodulin or SH3-domain-containing proteins, inter alia. In this study we used solid-state NMR (SSNMR) and Fourier transform infrared (FTIR) spectroscopy to study the conformation of 18.5 kDa MBP in association with actin microfilaments and bundles. FTIR spectroscopy of fully (13)C,(15)N-labeled MBP complexed with unlabeled F-actin showed induced folding of both protein partners, viz., some increase in beta-sheet content in actin, and increases in both alpha-helix and beta-sheet content in MBP, albeit with considerable extended structure remaining. Solid-state NMR spectroscopy revealed that MBP in MBP-actin assemblies is structurally heterogeneous but gains ordered secondary structure elements (both alpha-helical and beta-sheet), particularly in the terminal fragments and in a central immunodominant epitope. The overall conformational polymorphism of MBP is consistent with its in vivo roles as both a linker (membranes and cytoskeleton) and a putative signaling hub.
Ahmed
Mumdooh A M
MA
Department of Physics, University of Guelph, Guelph, Canada.
Bamm
Vladimir V
VV
Shi
Lichi
L
Steiner-Mosonyi
Marta
M
Dawson
John F
JF
Brown
Leonid
L
Harauz
George
G
Ladizhansky
Vladimir
V
D008841:Actin Cytoskeleton / Q000737:chemistry*; D000199:Actins / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens; D051379:Mice; D008969:Molecular Sequence Data; D004676:Myelin Basic Protein / Q000737:chemistry* / Q000235:genetics; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D020033:Protein Isoforms / Q000737:chemistry; D017433:Protein Structure, Secondary; D011522:Protons; D011994:Recombinant Proteins / Q000737:chemistry; D012492:Salts / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013696:Temperature
D000199:Actins; D004676:Myelin Basic Protein; D020033:Protein Isoforms; D011522:Protons; D011994:Recombinant Proteins; D012492:Salts