Structure of leech derived tryptase inhibitor (LDTI-C) in solution

• Published in: FEBS letters 1994-12, Vol.355 (3), p.290-296
• Main Authors: Mühlhahn, Peter, Czisch, Michael, Morenweiser, Robert, Habermann, Bianca, Engh, Richard A., Sommerhoff, Christian P., Auerswald, Ennes A., Holak, Tad A.
• Format: Article
• Language: English
• Subjects: 2D, two-dimensional; 3D, three-dimensional; Amino Acid Sequence; Animals; Annelida; Binding Sites; Computer Simulation; D2O, deuterated water; DQF-COSY, double quantum filtered homonuclear correlated spectroscopy; Genes, Synthetic; Hirudo medicinalis; Kazal-type serine proteinase inhibitor; LDTI, leech derived tryptase inhibitor; LDTI-C, form C of the leech derived tryptase inhibitor; Leech derived tryptase inhibitor; Leeches - chemistry; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Sequence Data; NOE, nuclear Overhauser effect; NOESY, two-dimensional NOE spectroscopy; Nuclear magnetic resonance; P1, P2, P3 and P1′, P2′, P3′, designate inhibitor residues amino-terminal and carboxy-terminal of the scissile peptide bond, respectively. NMR, nuclear magnetic resonance; Protease Inhibitors - chemistry; Protein Conformation; Protein Structure, Secondary; Proteins - chemistry; r.m.s., root-mean-square; Recombinant Proteins - chemistry; SA, simulated annealing; Solutions; Tertiary structure; TOCSY (HOHAHA), total correlation spectroscopy (homonuclear Hartmann-Hahn spectroscopy); Trypsin Inhibitor, Kazal Pancreatic - chemistry; Tryptase
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(94)01225-3

The three-dimensional solution structure of the leech derived tryptase inhibitor form C (LDTI-C), an inhibitor of 46 amino acids which contains 3 disulfide bridges, has been determined using 2D NMR spectroscopy. The 3D structure was determined on the basis of 262 interresidue interproton distance constraints derived from nuclear Overhauser enhancement measurements and 25 φ angles, supplemented by 3 ϕ and 15 χ1 angles. The core of LDTI-C is very well defined and consists of a short 3 10-helix-loop and a short two-stranded antiparallel β-sheet between residues 13–14 and 20–21. The N-terminus is fixed to the core by two disulfide bridges, while the C-terminus is connected to the β-sheet via the third disulfide bridge. The binding loop in LDTI exhibits lowest energy conformations belonging to the canonical conformation of serine proteinase inhibitors.