Amino acid sequencing of a trypsin inhibitor by refined 1.6 Å X-ray crystal structure of its complex with porcine β-trypsin

• Published in: FEBS letters 1992-02, Vol.297 (1), p.143-146
• Main Authors: Huang, Qichen, Liu, Shengping, Tang, Youqi, Zeng, Fuyue, Qian, Ruiqing
• Format: Article
• Language: English
• Subjects: Active site geometry; Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Animals; are indicated by an I after the residue number; Biological and medical sciences; Complex; Crystallography sequencing; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Hydrolases; inhibitor residues; isotropic temperature factor; MCTI; Molecular Sequence Data; Momordica charantia, Linn, trypsin inhibitor-A; Momordica charantia, Linn. trypsin inhibitor; Plant Proteins - genetics; Plant Proteins - metabolism; Protein Conformation; RMS; root-mean-square; Swine; Trypsin; Trypsin - metabolism; Trypsin Inhibitors - genetics; Trypsin Inhibitors - metabolism; X-Ray Diffraction
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(92)80346-I

The stoichiometric complex formed between porcine β-trypsin and the Momordica charantia, Linn. Cucurbitaceae trypsin inhibitor-A (MCTI-A) was crystallized and its X-ray crystal structure determined using molecular replacement method. The primary sequence and topology of the inhibitor was determined by recognizing the electron density and refined to a final R value of 0.167 (7.0—1.6 Å) with RMS deviation of bond lengths from standard values 0.012 Å. The sequence was compared with those obtained by other groups and was found to be similar to the squash proteinase inhibitor. Its spatial structure and the conformation of its primary binding segment from Cys-31 (P3) to Glu-71 (P3′) which contains the reactive scissile bond Arg-51 C-Ile-61 N were also very similar with other squash family proteinase inhibitors.