Three-dimensional structure of potato carboxypeptidase inhibitor in solution. A study using nuclear magnetic resonance, distance geometry, and restrained molecular dynamics
The solution conformation of potato carboxypeptidase inhibitor (CPI) has been investigated by /sup 1/H NMR spectroscopy. The spectrum is assigned in a sequential manner by using two-dimensional NMR techniques to identify through-bond and through-space (<5 A) connectivities. A set of 309 approximate interproton distance restraints is derived from the two-dimensional nuclear Overhauser enhancement spectra and used as the basis of a three-dimensional structure determination by a combination of metric matrix distance geometry and restrained molecular dynamics calculations. A total of 11 converged distance geometry structures were computed and refined by using restrained molecular dynamics. The average atomic root mean square (rms) difference between the final 11 structures and the mean structure obtained by averaging their coordinates is 1.4 +/- 0.3 A for residues 2-39 and 0.9 +/- 0.2 A for residues 5-37. The corresponding values for all atoms are 1.9 +/- 0.3 and 1.4 +/- 0.2 A, respectively. The computed structures are very close to the X-ray structure of CPI in its complex with carboxypeptidase, and the backbone atomic rms difference between the mean of the computed structures and the X-ray structure is only 1.2 A. Nevertheless, there are some real differences present which are evidenced by significant deviations between the experimental upper interproton distance limits and the corresponding interproton distances derived from the X-ray structure. These principally occur in two regions, residues 18-20 and residues 28-30, the latter comprising part of the region of secondary contact between CPI and carboxypeptidase in the X-ray structure.
- Research Organization:
- Max-Planck-Institut fuer Biochemie, Muenchen, Germany, F.R.
- OSTI ID:
- 5301848
- Journal Information:
- Biochemistry; (United States), Vol. 26:24
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CARBOXYPEPTIDASES
BIOCHEMISTRY
ENZYME INHIBITORS
NUCLEAR MAGNETIC RESONANCE
STRUCTURAL CHEMICAL ANALYSIS
GEOMETRY
X-RAY DIFFRACTION
CHEMISTRY
COHERENT SCATTERING
DIFFRACTION
ENZYMES
HYDROLASES
MAGNETIC RESONANCE
MATHEMATICS
PEPTIDE HYDROLASES
RESONANCE
SCATTERING
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