Nuclear magnetic resonance studies of trypsin inhibitors isolated from seeds of Cucurbitaceae plants

Journal Article · Thu May 01 00:00:00 EDT 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:7189877

Sobczyk, K; Markley, J L

Two-dimensional NMR techniques were used to assign individual protons in two trypsin inhibitors isolated from squash seeds (Cucurbita maxima and C. pepo). The assignments of /sup 1/H NMR signals from these unusually small proteins (29 amino acid residues) were based entirely on the sequences of the proteins plus the analysis of data from two-dimensional /sup 1/H)/sup 1/H) chemical shift correlation spectroscopy (COSY), relayed COSY, and nuclear Overhauser effect spectroscopy (NOESY). The pH dependence (pH range 1 to 12) of NMR chemical shifts has been analyzed in detail. The complex pH titration profiles exhibited by the /sup 1/H peaks of His-25 and Tyr-27 may be interpreted in terms of side-chain interactions between these residues. The protons of Gly-26 demonstrate a well-resolved AB spin system. These results suggest that this region of the protein has restricted conformational freedom. The kinetics of amide hydrogen/deuterium exchange were measured as a function of pH. The exchange rate for all amide hydrogens is governed by acid/base catalysis.

• Research Organization: Univ. of Wisconsin, Madison
• OSTI ID: 7189877
• Report Number(s): CONF-8606151-
• Journal Information: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Vol. 45:6; ISSN FEPRA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
550600 -- Medicine
59 BASIC BIOLOGICAL SCIENCES
62 RADIOLOGY AND NUCLEAR MEDICINE
CHEMICAL SHIFT
ENZYME INHIBITORS
ENZYMES
HYDROLASES
MAGNETIC RESONANCE
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
ORGANIC COMPOUNDS
PEPTIDE HYDROLASES
PROTEIN STRUCTURE
PROTEINS
RESONANCE
SEEDS
SERINE PROTEINASES
SPECTRA
TRYPSIN