title: Molten globule state of tear lipocalin: ANS binding restores tertiary interactions.
abstract: Tear lipocalin (TL) may stabilize the lipid layer of tears through a molten globule state triggered by low pH. EPR spectroscopy with site-directed spin labeling, revealed the side chain mobility of residues on the G-strand of TL in a molten globule state; the G-strand retains beta-sheet structure. All of the side chains of G-strand residues become more loosely packed, especially residues 96-99. In contrast, the highly mobile side chain of residue 95 on the F-G loop, becomes tightly packed. ANS binding to TL in a molten globule state reestablishes tight packing around side chains that are oriented both inside and outside of the barrel. Unlike RBP and BLG; TL has no disulfide bond between G- and H-strands. It is likely that the central beta-sheet in the molten globule state of lipocalins is stabilized by its interactions with the main alpha-helix, rather than the interstrand disulfide bond.
authors: Department of Pathology, UCLA School of Medicine, Jules Stein Eye Institute, 100 Stein Plaza, Los Angeles, CA 90095, USA.
authors: Oktay K
authors: OK
authors: Gasymov
authors: Adil R
authors: AR
authors: Abduragimov
authors: Ben J
authors: BJ
authors: Glasgow
mesh_terms: D000817:Anilino Naphthalenesulfonates / Q000737:chemistry*; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D054835:Lipocalin 1; D008956:Models, Chemical; D008958:Models, Molecular; D044367:Phase Transition; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship; D013696:Temperature
chemical_list: D000817:Anilino Naphthalenesulfonates; D002352:Carrier Proteins; D054835:Lipocalin 1; C027132:1-anilino-8-naphthalenesulfonate