1xki
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Crystal structure of human tear lipocalin/von Ebners gland protein
OverviewOverview
In contrast with earlier assumptions, which classified human tear, lipocalin (Tlc) as an outlier member of the lipocalin protein family, the, 1.8-A resolution crystal structure of the recombinant apoprotein confirms, the typical eight-stranded antiparallel beta-barrel architecture with an, alpha-helix attached to it. The fold of Tlc most closely resembles the, bovine dander allergen Bos d 2, a well characterized prototypic lipocalin, but also reveals similarity with beta-lactoglobulin. However, compared, with other lipocalin structures Tlc exhibits an extremely wide ligand, pocket, whose entrance is formed by four partially disordered loops. The, cavity deeply extends into the beta-barrel structure, where it ends in two, distinct lobes. This unusual structural feature explains the known, promiscuity of Tlc for various ligands, with chemical structures ranging, from lipids and retinoids to the macrocyclic antibiotic rifampin and even, to microbial siderophores. Notably, earlier findings of biological, activity as a thiol protease inhibitor have no correspondence in the, three-dimensional structure of Tlc, rather it appears that its proteolytic, fragments could be responsible for this phenomenon. Hence, the present, structural analysis sheds new light on the ligand binding activity of this, functionally obscure but abundant human lipocalin.
About this StructureAbout this Structure
1XKI is a Single protein structure of sequence from Homo sapiens with ZN and CL as ligands. Full crystallographic information is available from OCA.
ReferenceReference
The 1.8-A crystal structure of human tear lipocalin reveals an extended branched cavity with capacity for multiple ligands., Breustedt DA, Korndorfer IP, Redl B, Skerra A, J Biol Chem. 2005 Jan 7;280(1):484-93. Epub 2004 Oct 15. PMID:15489503
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