Fig. 3: Interaction of OSH6 with the C-terminal region of IST2.
From: Structural basis for lipid transport at membrane contact sites by the IST2–OSH6 complex
a, Binding of a peptide encompassing residues 732–761 of IST2 (IST2732−761) to OSH6. Binding isotherms were obtained from the titration of IST2732−761 to OSH6. The data show a fit to a single-binding-site model line with a Kd of 694.4 ± 54.2 nM. Errors represent fitting errors. Inset, thermogram. b, Ribbon representation of the structure of the OSH6–IST2732−761 complex determined by X-ray crystallography at 1.84 Å. IST2732−761 is colored in yellow and the N-terminal lid helix of OSH6 is colored in green. A bound PS molecule is displayed in light blue. c, The 2Fo − Fc density of the refined structure superimposed on a model of the IST2-binding region. Left, density from the OSH6–IST2732−761 complex defining the conformation of residues 732–758 of the peptide. Right, density of the OSH6 complex with the shorter IST2732−756 peptide determined at 1.94 Å defining the conformation of residues 732–750 of the peptide. The sequence of the IST2732−761 peptide is shown below. d, Sections of the OSH6–IST2 interactions revealed in the OSH6–IST2732−761 complex. A model of the well-defined parts of the IST2732−756 peptide in stick representation, with its interacting region of OSH6 represented as ribbon. Different regions of the interaction are indicated as shaded areas and shown as zoomed-in views in e–g with OSH6 represented as sticks. e–g, Sections of the OSH6–IST2 interactions highlighted in d in relation to the OSH6-binding sequence on IST2: N-terminal region (e), center (f) and C-terminal region (g). h, The 2Fo − Fc density of the bound PS lipid (left) and lipid-binding region of OSH6, with interacting side chains shown as sticks.
