Proton NMR spectroscopic characterization of binary and ternary complexes of cobalt(II) carboxypeptidase A with inhibitors

Journal Article · Tue Nov 01 00:00:00 EST 1988 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00422a005· OSTI ID:5981531

Bertini, I; Luchinat, C; Messori, L; Monnanni, R; Auld, D S; Riordan, J F

The binding of L- and D-phenylalanine and carboxylate inhibitors to cobalt(II)-substituted carboxypeptidase A, Co(II)CPD (E), in the presence and absence of pseudohalogens (X = N/sub 3//sup -/, NCO/sup -/, and NCS/sup -/) has been studied by /sup 1/H NMR spectroscopy. This technique monitors the proton signals of histidine residues bound to cobalt(II) and is therefore sensitive to the interactions of inhibitors that perturb the coordination sphere of the metal. Enzyme-inhibitor complexes, E/times/I, E/times/I/sub 2/, and E/times/I/times/X, each with characteristic NMR features, have been identified. The NMR data suggest that when the carboxylate group of a substrate of inhibitor binds at the active site, a conformational change occurs that allows a second ligand molecule to bind to the metal ion, altering its coordination sphere and thereby attenuating the bidentate behavior of Glu-72. The /sup 1/H NMR signals also reflect alterations in the histidine interactions with the metal upon inhibitor binding. Isotropic shifts in the signals for the C-4 (c) and N protons (a) of one of the histidine ligands are readily observed in all of these complexes. These signals are relatively constant for all E/times/I and E/times/I/times/X complexes, indicating that this ligand is in a relatively fixed or buried conformation. However in the 2:1 carboxylate inhibitor (E/times/I/sub 2/) complexes, both signals are shifted upfield, suggesting a disturbance in the interaction of this histidine with the metal.

• Research Organization: Univ. of Florence (Italy)
• OSTI ID: 5981531
• Journal Information: Biochemistry; (United States), Vol. 27:22
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
CARBOXYPEPTIDASES
CONFIGURATION INTERACTION
NUCLEAR MAGNETIC RESONANCE
ENZYME INHIBITORS
ACETATES
CATTLE
COBALT COMPLEXES
HISTIDINE
METALLOPROTEINS
PHENYLALANINE
PROTONS
SPECTRAL SHIFT
AMINO ACIDS
ANIMALS
AZOLES
BARYONS
CARBOXYLIC ACID SALTS
CARBOXYLIC ACIDS
COMPLEXES
DOMESTIC ANIMALS
ELEMENTARY PARTICLES
ENZYMES
FERMIONS
HADRONS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROLASES
IMIDAZOLES
MAGNETIC RESONANCE
MAMMALS
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PEPTIDE HYDROLASES
PROTEINS
RESONANCE
RUMINANTS
TRANSITION ELEMENT COMPLEXES
VERTEBRATES
550601* - Medicine- Unsealed Radionuclides in Diagnostics