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Assignment of the 13 C‐nmr spectra of virgin and reactive‐site modified turkey ovomucoid third domain
Author(s) -
Robertson A. D.,
Rhyu G. I.,
Westler W. M.,
Markley J. L.
Publication year - 1990
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360290216
Subject(s) - chemistry , chemical shift , peptide bond , peptide , side chain , hydrolysis , nuclear magnetic resonance spectroscopy , stereochemistry , trypsin , nmr spectra database , crystallography , hydrogen bond , molecule , spectral line , enzyme , organic chemistry , biochemistry , polymer , physics , astronomy
The virgin (reactive‐site Leu 18 ‐Glu 19 peptide bond intact) and modified (reactive‐site Leu 18 ‐Glu 19 peptide bond hydrolyzed) forms of turkey ovomucoid third domain (OMTKY3 and OMTKY3*, respectively) have been analyzed by proton‐detected 1 H{ 13 C} two‐dimensional single‐bond correlation ( 1 H{ 13 C}SBC) spectroscopy. Previous 1 H‐nmr assignments of these proteins [A. D. Robertson, W. M. Westler, and J. L. Markley (1988) Biochemistry , 27 , 2519–2529; G. I. Rhyu and J. L. Markley (1988) Biochemistry , 27 , 2529–2539] have been extended to directly bonded 13 C atoms. Assignments have been made to 52 of the 56 backbone 13 C α ‐ 1 H units and numerous side‐chain 13 C‐ 1 H groups in both OMTKY3 and OMTKY3*. The largest changes in the 13 C chemical shift upon conversion of OMTKY3 to OMTKY3* occur at or near the reactive site, and tend toward values observed in small peptides. Moreover, the side‐chain prochiral methylene protons attached to the C γ of Glu 19 and C δ of Arg 21 show nonequivalent chemical shifts in OMTKY3 but more equivalent chemical shift in OMTKY3*. These results suggest that the reactive site region becomes less ordered upon hydrolysis of the Leu 18 ‐Glu 19 peptide bond. Comparison of 13 C α chemical shifts of OMTKY3 and bovine pancreatic trypsin inhibitor [D. Brühuiler and G. Wagner (1986) Biochemistry 25 , 5839–5843; N. R. Nirmala and G. Wagner (1988) Journal of the American Chemical Society , 110 , 7557–7558] with small peptide values [R. Richarz and K. Wüthrich (1978) Biopolymers , 17 , 2133–2141] suggests that 13 C α chemical shifts of residues residing in helices are generally about 2 ppm downfield of resonances from nonhelical residues.