Heterogeneous packing in the folding/unfolding intermediate state of bitter gourd trypsin inhibitor.
The conformation and dynamics of a protein are essential in characterizing the protein folding/unfolding intermediate state. They are closely involved in the packing and site-specific interactions of peptide elements to build and stabilize the tertiary structure of the protein. In this study, it was confirmed that trypsin inhibitor obtained from seeds of bitter gourd (BGTI) adopted a peculiar but plausible conformation and dynamics in the unfolding intermediate state. The fluorescence spectrum of one of two tryptophan residues of BGTI, Trp9, shifted to the blue side in the presence of 2-3 M guanidine hydrochloride, although the other, Trp54, did not show this spectral shift. At the same time, the motional freedom of Trp9 revealed by a time-resolved fluorescence study decreased, suggesting that the segmental motion of this residue was more restricted. These results indicate that BGTI takes such a conformation state that the hydrophobic core and loop domains arranging Trp9 and Trp54 respectively are heterogeneously packed in the unfolding intermediate state.
Institute of Biophysics, Faculty of Agriculture, Kyushu University, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
Daisuke
D
Takahashi
Shuzo
S
Matsumoto
Etsuko
E
Nishimoto
Takuhiro
T
Otosu
Shoji
S
Yamashita
D002942:Circular Dichroism; D008958:Models, Molecular; D029777:Momordica charantia / Q000737:chemistry* / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013816:Thermodynamics; D014361:Trypsin Inhibitors / Q000737:chemistry* / Q000378:metabolism*
D010940:Plant Proteins; D014361:Trypsin Inhibitors