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Compact Packing of Lipocalin-type Prostaglandin D Synthase Induced by Binding of Lipophilic Ligands

DOI: 10.1093/jb/mvn154 DOI Help

Authors: Katsuaki Inoue (Diamond Light Source) , Naoto Yagi (SPring-8/JASRI) , Yoshihiro Urade (Osaka Bioscience Institute) , Takashi Inui (Osaka Prefecture University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Biological Chemistry , VOL 145(2) , PAGES 169-175

State: Published (Approved)
Published: October 2008

Abstract: Lipocalin-type prostaglandin (PG) D synthase (L-PGDS) is a multi-functioning protein belonging to the lipocalin family, acting as a PGD2-synthesizing enzyme and as an extracellular transporter for small lipophilic molecules. In the present study, to clarify the conformational changes of lipocalin proteins induced by binding of lipophilic ligands, such as all-trans-retinoic acid (RA), bilirubin (BR) and biliverdin (BV), we measured small-angle X-ray scattering (SAXS) of L-PGDS and that of two other lipocalins, ?-lactoglobulin (?LG) and retinol-binding protein (RBP). L-PGDS bound all three ligands with high affinity, while ?LG and RBP could bind only RA. The radius of gyration was estimated to be 19.4 Å for L-PGDS, and 18.8 Å for L-PGDS/RA, 17.3 Å for L-PGDS/BR and 17.8 Å for L-PGDS/BV complexes, indicating that L-PGDS became compact after binding of these ligands. Alternatively, the radius of gyration of ?LG and RBP was 20.3 and 26.2 Å, respectively, and was almost the same before and after RA binding. Based on the SAXS data, we found that the compact packing upon binding ligands is a special feature of L-PGDS and it may be ascribed to the conformational flexibility of L-PGDS molecule itself, which underlies the high-affinity for its ligands.

Journal Keywords: Broad Selectivity; Compact Packing; Conformational Change; Radius Of Gyration; Saxs

Subject Areas: Biology and Bio-materials, Physics, Medicine

Instruments: NONE-No attached Diamond beamline