NMR chemical shift mapping of the binding site of a protein proteinase inhibitor: changes in the 1H, 13C and 15N NMR chemical shifts of turkey ovomucoid third domain upon binding to bovine chymotrypsin Aα

✍ Scribed by Jikui Song; John L. Markley

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 201 KB
• Volume: 14
• Category: Article
• ISSN: 0952-3499
• DOI: 10.1002/jmr.530

✦ Synopsis

Abstract

The substrate‐like inhibition of serine proteinases by avian ovomucoid domains has provided an excellent model for protein inhibitor‐proteinase interactions of the standard type. ^1^H,^15^N and ^13^C NMR studies have been undertaken on complexes formed between turkey ovomucoid third domain (OMTKY3)^2^ and chymotrypsin A~α~ (Ctr) in order to characterize structural changes occurring in the Ctr binding site of OMTKY3. ^15^N and ^13^C were incorporated uniformly into OMTKY3, allowing backbone resonances to be assigned for OMTKY3 in both its free and complex states. Chemical shift perturbation mapping indicates that the two regions, K13‐P22 and N33‐A40, are the primary sites in OMTKY3 involved in Ctr binding, in full agreement with the 12 consensus proteinase‐contact residues of OMTKY3 defined previously on the basis of X‐ray crystallographic and mutational analysis. Smaller chemical shift perturbations in selected other regions may result from minor structural changes on binding. Through‐bond ^15^N–^13^C correlations between P1‐^13^C′ and P1′‐^15^N in two‐dimensional H(N)CO and HN(CO) NMR spectra of selectively labeled OMTKY3 complexed with Ctr indicate that the scissile peptide bond between L18 and E19 of the inhibitor is intact in the complex. The chemical shifts of the reactive site peptide bond indicate that it is predominantly trigonal, although the data are not inconsistent with a slight perturbation of the hybridization of the peptide bond toward the first tetrahedral state along the reaction coordinate. Copyright © 2001 John Wiley & Sons, Ltd.

Abbreviations used:

BPTI

bovine pancreatic trypsin inhibitor, Swiss‐Prot P00974

Ctr

bovine chymotrypsin A~α~ Swiss‐Prot P00766

OMTKY3

third domain of the proteinase inhibitor (ovomucoid) from turkey (Meleagris gallopavo), Swiss‐Prot P01004

SSI

streptomyces subtilisin inhibitor, Swiss‐Prot P01006

STI

soybean trypsin inhibitor, Swiss‐Prot P01071.