Fine mapping of the amyloid ?-protein binding site on myelin basic protein.

ABSTRACT: The assembly and deposition of amyloid ?-protein (A?) in brain is a key pathological feature of Alzheimer's disease and related disorders. Factors have been identified that can either promote or inhibit A? assembly in brain. We previously reported that myelin basic protein (MBP) is a potent inhibitor of A? fibrillar assembly [Hoos, M. D., et al. (2007) J. Biol. Chem. 282, 9952-9961; Hoos, M. D., et al. (2009) Biochemistry 48, 4720-4727]. Moreover, the region on MBP responsible for this activity was localized to the 64 N-terminal amino acids (MBP1-64) [Liao, M. C., et al. (2010) J. Biol. Chem. 285, 35590-35598]. In the study presented here, we sought to further define the site on MBP1-64 involved in this activity. Deletion mapping studies showed that the C-terminal region (residues 54-64) is required for the ability of MBP1-64 to bind A? and inhibit fibril assembly. Alanine scanning mutagenesis revealed that amino acids K54, R55, G56, and K59 within MBP1-64 are important for both A? binding and inhibition of fibril assembly as assessed by solid phase binding, thioflavin T binding and fluorescence, and transmission electron microscopy studies. Strong spectral shifts are observed by solution nuclear magnetic resonance spectroscopy of specific N-terminal residues (E3, R5, D7, E11, and Q15) of A?42 upon the interaction with MBP1-64. Although the C-terminal region of MBP1-64 is required for interactions with A?, a synthetic MBP50-64 peptide was itself devoid of activity. These studies identify key residues in MBP and A? involved in their interactions and provide structural insight into how MBP regulates A? fibrillar assembly.

SUBMITTER: Kotarba AE 

PROVIDER: S-EPMC3640357 | biostudies-literature | 2013 Apr

REPOSITORIES: biostudies-literature