Reference : Secondary structure and solvent accessibility of a calmodulin-binding C-terminal segm...
Scientific journals : Article
Life sciences : Biochemistry, biophysics & molecular biology
Secondary structure and solvent accessibility of a calmodulin-binding C-terminal segment of membrane-associated myelin basic protein.
Homchaudhuri, Lopamudra [> >]
De Avila, Miguel [> >]
Nilsson, Stina B. [> >]
Bessonov, Kyrylo mailto [Université de Liège - ULiège > Dép. d'électric., électron. et informat. (Inst.Montefiore) > Bioinformatique >]
Smith, Graham S. T. [> >]
Bamm, Vladimir V. [> >]
Musse, Abdiwahab A. [> >]
Harauz, George [> >]
Boggs, Joan M. [> >]
Yes (verified by ORBi)
United States
[en] Animals ; Binding Sites ; Calcium/chemistry/metabolism ; Calmodulin/chemistry/genetics/metabolism ; Mice ; Myelin Basic Protein/chemistry/genetics/metabolism ; Protein Binding ; Protein Structure, Secondary ; Protein Structure, Tertiary
[en] Myelin basic protein (MBP), specifically the 18.5 kDa isoform, is a peripheral membrane protein and a major component of mammalian central nervous system myelin. It is an intrinsically disordered and multifunctional protein that binds cytoskeletal and other cytosolic proteins to a membrane surface and thereby acquires ordered structure. These associations are modulated by post-translational modifications of MBP, as well as by interactions of MBP with Ca(2+)-calmodulin (CaM). Enzymatic deimination of usually six arginine residues to citrulline results in a decrease in the net positive charge of the protein from 19 to </=13. This deiminated form is found in greater amounts in normal children and in adult patients with the demyelinating disease multiple sclerosis. In this paper, we examine the secondary structure of a calmodulin-binding domain, residues A141-L154, when associated with a lipid bilayer in recombinant murine 18.5 kDa forms rmC1 (unmodified) and rmC8 (pseudodeiminated). We demonstrate here by site-directed spin labeling and electron paramagnetic resonance (EPR) spectroscopy that the Y142-L154 segment in membrane-associated rmC1 forms an amphipathic alpha-helix, with high accessibility to O(2) and low accessibility to NiEDDA. In membrane-associated rmC8, this segment assumed a structure distorted from an alpha-helix. Spin-labeled residues in rmC1 in solution were more immobilized on binding Ca(2+)-CaM than those in rmC8. Furthermore, rmC8 was dissociated more readily from a lipid bilayer by Ca(2+)-CaM than was rmC1. These results confirm both a predicted induced ordering upon membrane association in a specific segment of 18.5 kDa MBP, and that this segment is a CaM-binding site, with both interactions weakened by deimination of residues outside of this segment. The deiminated form would be more susceptible to regulation of its membrane binding functions by Ca(2+)-CaM than the unmodified form.

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