1tin
From Proteopedia
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THREE-DIMENSIONAL STRUCTURE IN SOLUTION OF CUCURBITA MAXIMA TRYPSIN INHIBITOR-V DETERMINED BY NMR SPECTROSCOPY
Overview
The solution structure of Cucurbita maxima trypsin inhibitor-V (CMTI-V), which is also a specific inhibitor of the blood coagulation protein, factor XIIa, was determined by 1H NMR spectroscopy in combination with a, distance-geometry and simulated annealing algorithm. Sequence-specific, resonance assignments were made for all the main-chain and most of the, side-chain hydrogens. Stereospecific assignments were also made for some, of the beta-, gamma-, delta-, and epsilon-hydrogens and valine methyl, hydrogens. The ring conformations of all six prolines in the inhibitor, were determined on the basis of 1H-1H vicinal coupling constant patterns;, most of the proline ring hydrogens were stereospecifically assigned on the, basis of vicinal coupling constant and intraresidue nuclear Overhauser, effect (NOE) patterns. Distance constraints were determined on the basis, of NOEs between pairs of hydrogens. Dihedral angle constraints were, determined from estimates of scalar coupling constants and intraresidue, NOEs. On the basis of 727 interproton distance and 111 torsion angle, constraints, which included backbone phi angles and side-chain chi 1, chi, 2, chi 3, and chi 4 angles, 22 structures were calculated by a distance, geometry algorithm and refined by energy minimization and simulated, annealing methods. Both main-chain and side-chain atoms are well-defined, except for a loop region, two terminal residues, and some side-chain atoms, located on the molecular surface. The average root mean squared deviation, in the position for equivalent atoms between the 22 individual structures, and the mean structure obtained by averaging their coordinates is 0.58 +/-, 0.06 A for the main-chain atoms and 1.01 +/- 0.07 A for all the, non-hydrogen atoms of residues 3-40 and 49-67. These structures were, compared to the X-ray crystallographic structure of another protein of the, same inhibitor family-chymotrypsin inhibitor-2 from barley seeds [CI-2;, McPhalen, C. A., & James, M. N. G. (1987) Biochemistry 26, 261-269]. The, main-chain folding patterns are highly similar for the two proteins, which, possess 62% sequence differences. However, major differences are noted in, the N- and C-terminal segments, which may be due to the presence of a, disulfide bridge in CMTI-V, but not in CI-2.
About this Structure
1TIN is a Single protein structure of sequence from Cucurbita maxima with ACE as ligand. Full crystallographic information is available from OCA.
Reference
Three-dimensional solution structure of Cucurbita maxima trypsin inhibitor-V determined by NMR spectroscopy., Cai M, Gong Y, Kao JL, Krishnamoorthi R, Biochemistry. 1995 Apr 18;34(15):5201-11. PMID:7711040
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