High-resolution proton and laser photochemically induced dynamic nuclear polarization NMR studies of cation binding to bovine. cap alpha. -lactalbumin

Journal Article · Tue Sep 08 00:00:00 EDT 1987 · Biochemistry; (United States)

OSTI ID:5878217

Berliner, L J; Koga, K; Nishikawa, H; Scheffler, J E

..cap alpha..-Lactalbumin (..cap alpha..-LA) is a calcium binding protein that also binds Mn(II), lanthanide ions, Al(III), Zn(II), Co(II). The structural implications of cation binding were studied by high-resolution proton (200 MHz) NMR and photochemically induced dynamic nuclear polarization (CIDNP) spectroscopy. Marked changes were observed in the NMR spectra of the apoprotein upon addition of a stoichiometric amount of calcium to yield Ca(II)-..cap alpha..-LA, manifested particularly in ring current shifted aliphatic peaks and in several shifts in the aromatic region, all of which were under slow exchange conditions. The CIDNP results showed that two surface-accessible tyrosine residues, assigned as Tyr-18 and -36, became inaccessible to the solvent upon addition of 1:1 Ca(II) to apo-..cap alpha..-lactalbumin, while Tyr-103 and Trp-104 remained completely accessible in both conformers. The proton NMR spectra of apo-..cap alpha..-LA and Al(III)-..cap alpha..-LA were extremely similar, which was also consistent with intrinsic fluorescence results. The paramagnetic cation Mn(II) bound to the strong calcium binding site on apo-..cap alpha..-LA but also to the weak secondary Ca(II) binding site(s) on Ca(II)-..cap alpha..-LA. It was also found that Co(II) bound to some secondary sites on Ca(II)-..cap alpha..-LA that overlapped the weak calcium site. All of the lanthanide shift reagents (Pr(III), Eu(III), Tb(III), Dy(III), Tm(III), and Yb(III)) bound under slow exchange conditions; their relative affinities for apo-..cap alpha..-lactalbumin from competitive binding experiments were Dy(III), Tb(III), and Pr(III) > Ca(II) > Yb(III).

• Research Organization: Ohio State Univ., Columbus
• OSTI ID: 5878217
• Journal Information: Biochemistry; (United States), Vol. 26:18
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
ALBUMINS
CONFIGURATION INTERACTION
NUCLEAR MAGNETIC RESONANCE
POLARIZATION
CATIONS
CALCIUM COMPOUNDS
CATTLE
HEXOSYL TRANSFERASES
MANGANESE COMPOUNDS
PROTONS
RARE EARTHS
ALKALINE EARTH METAL COMPOUNDS
ANIMALS
BARYONS
CHARGED PARTICLES
DOMESTIC ANIMALS
ELEMENTARY PARTICLES
ELEMENTS
ENZYMES
FERMIONS
GLYCOSYL TRANSFERASES
HADRONS
IONS
MAGNETIC RESONANCE
MAMMALS
METALS
NUCLEONS
ORGANIC COMPOUNDS
PROTEINS
RESONANCE
RUMINANTS
TRANSFERASES
TRANSITION ELEMENT COMPOUNDS
VERTEBRATES
550601* - Medicine- Unsealed Radionuclides in Diagnostics