NMR structure of the sterol carrier protein-2: Implications for the biological role

The determination of the NMR structure of the sterol carrier protein-2 (SCP2), analysis of backbone ¹⁵N spin relaxation parameters and NMR studies of nitroxide spin-labeled substrate binding are presented as a new basis for Investigations of the mode of action of SCP2. The SCP2 fold is formed by a five-stranded β-sheet and four α-helices. Fatty acid binding to a hydrophobic surface area formed by amino acid residues of the first and third helices, and the β-sheet, which are all located in the polypeptide segment 8-102, was identified with the use of the spinlabeled substrate 16-doxylstearic acid. In the free protein, the lipid-binding site is covered by the C-terminal segment 105-123, suggesting that this polypeptide segment, which carries the peroxisomal targeting signal (PTS1), might be involved in the regulation of ligand binding. (C) 2000 Academic Press.