Residue 19 of tryptophan in bovine β-lactoglobulin (β-LG) is the only invariant residue throughout the lipocalin superfamily having two characteristic features: binding ability for small hydrophobic molecules and the unique β-barrel three-dimensional structure. In this study, we investigated whether this strictly conserved Trp-19 of β-LG would be indispensable for its structure and function such as maintaining the molecular structure and biological activity of β-LG. Spectroscopic and enzymatic oxidation experiments on retinol bound to W19Y, in which Tyr was substituted for Trp-19, showed that Trp-19 was not critical for this binding, but was important for stably maintaining the environment surrounding retinol and the bound retinol. An analysis, using four anti-β-LG monoclonal antibodies as probes, revealed a structural change in region 20-29, but not in the reverse region of Trp-19. A guanidine hydrochloride-induced unfolding study showed that the conformational stability of W19Y was greatly reduced by 6.9 kcal/mol compared to that of wild-type β-LG. These facts indicated that Trp-19 is one of the important residues in correctly maintaining the local structure of β-LG and stably retaining its overall structure, thereby conserving the bound retinol molecule.
|Number of pages||10|
|Journal||Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology|
|Publication status||Published - Jul 20 1994|
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Structural Biology