Details

Autor(en) / Beteiligte

• Yamasaki, Masayuki
• Takahashi, Nobuyuki
• Hirose, Masaaki

Titel

Crystal Structure of S-ovalbumin as a Non-loop-inserted Thermostabilized Serpin Form

Ist Teil von

• The Journal of biological chemistry, 2003-09, Vol.278 (37), p.35524-35530

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2003

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Ovalbumin, a non-inhibitory member of serine proteinase inhibitors (serpin), is transformed into a heat-stabilized form, S-ovalbumin, under elevated pH conditions. The structural mechanism for the S-ovalbumin formation has long been a puzzling question in food science and serpin structural biology. On the basis of the commonly observed serpin thermostabilization by insertion of the reactive center loop into the proximal β-sheet, the most widely accepted hypothetical model has included partial loop insertion. Here we demonstrate, for the first time, the crystal structure of S-ovalbumin at 1.9-Å resolution. This structure unequivocally excludes the partial loop insertion mechanism; the overall structure, including the reactive center loop structure, is almost the same as that of native ovalbumin, except for the significant motion of the preceding loop of strand 1A away from strand 2A. The most striking finding is that Ser-164, Ser-236, and Ser-320 take the d-amino acid residue configuration. These chemical inversions can be directly related to the irreversible and stepwise nature of the transformation from native ovalbumin to S-ovalbumin. As conformational changes of the side chains, significant alternations are found in the values of the χ1 of Phe-99 and the χ3 of Met-241. The former conformational change leads to the decreased solvent accessibility of the hydrophobic core around Phe-99, which includes Phe-180 and Phe-378, the highly conserved residues in serpin. This may give a thermodynamic advantage to the structural stability of S-ovalbumin.