NMR determination of the secondary structure and the three-dimensional polypeptide backbone fold of the human sterol carrier protein 2.
Nuclear magnetic resonance (NMR) spectroscopy was used to determine the secondary structure and the three-dimensional polypeptide backbone fold of the human sterol carrier protein 2 (hSCP2), which is a basic protein with 123 residues believed to participate in the intracellular transport of cholesterol and various other lipids. Sequence-specific assignments were obtained for nearly all backbone 1H and 15N resonances, as well as for about two-thirds of the side-chain 1H resonances, using uniform 15N-labeling of the protein combined with homonuclear two-dimensional 1H NMR and three-dimensional 15N-correlated 1H NMR. Three alpha-helices comprising the polypeptide segments of residues 9-22, 25-30 and 78-84 were identified by sequential and medium-range nuclear Overhauser effects (NOE). The analysis of long-range backbone-backbone NOEs showed that hSCP2 further contains a five-stranded beta-sheet including the residues 33-41, 47-54, 60-62, 71-76 and 100-102, which is a central feature of the molecular architecture. The first three strands are arranged in an antiparallel fashion, the polypeptide chain then crosses over this three-stranded sheet in a right-handed sense so that the fourth strand is added parallel to the first one. The fifth strand runs antiparallel to the fourth one, so that the overall topology is +1, +1, -3x, -1. The three-dimensional arrangement of the beta-sheet and the first two helices was determined using an input of 625 NOE upper distance constraints and 95 scalar coupling constants for a preliminary structure calculation with the distance geometry program DIANA.
Szyperski
T
T
Institut für Molekularbiologie und Biophysik, Eidgenössische Technische Hochschule-Hönggerberg, Zürich, Switzerland.
Scheek
S
S
Johansson
J
J
Assmann
G
G
Seedorf
U
U
Wüthrich
K
K
D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry*; D002942:Circular Dichroism; D006358:Hot Temperature; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D010940:Plant Proteins; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary
D002352:Carrier Proteins; D010940:Plant Proteins; C072087:sterol carrier proteins