sup 19 F NMR studies of the D-galactose chemosensory receptor. 2. Ca(II) binding yields a local structural change

Journal Article · Tue Apr 30 00:00:00 EDT 1991 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00231a022· OSTI ID:5594932

Luck, L A; Falke, J J ^[1]

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1. Univ. of Colorado, Boulder (USA)

The Escherichia coli D-galactose and D-glucose receptor possesses a Ca(II)-binding site closely related in structure and metal-binding characteristics to the eukaryotic EF-hand sites. Only the structure of the Ca(II)-occupied site is known. To investigate the structural change triggered by Ca(II) and Sr(II) binding, the authors have used {sup 19}F NMR to probe five 5-fluorotryptophan (5F-Trp) and seven 3-fluorophenylalanine (3F-Phe) positions in the structure. Of particular interest were two 5F-Trp residues near the N terminus of the Ca(II) site at positions 127 and 133 resonances, indicating a detectable structural change in the Ca(II) site. When the metal was removed from the Ca(II) site, the 5F-Trp127 and -133 frequencies shifted to a new value similar to that observed for free 5F-Trp in aqueous solvent, and this new frequency was a function of the H{sub 2}O to D{sub 2}O ratio, indicating that the residues had become solvent exposed. The allosteric coupling of the metal and sugar binding sites was observed to be slight. Together the results indicate that the structural changes in the Ca(II) site are primarily localized in the region of the site. Removal of the metal ion from the site exposes the nearby 5F-Trp127 and -133 residues to the solvent, suggesting that the empty site has a more open structure. Evidence for a similar opening of eukaryotic EF-hand sites to solvent upon removal of metal is discussed. Such a structural change could play an important role in facilitating substrate binding and dissociation.

• OSTI ID: 5594932
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 30:17; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
ALDEHYDES
ALKALINE EARTH METAL COMPOUNDS
AMINO ACIDS
AROMATICS
AZAARENES
AZOLES
CALCIUM COMPOUNDS
CARBOHYDRATES
CARBOXYLIC ACIDS
CATIONS
CELL CONSTITUENTS
CELL MEMBRANES
CHARGED PARTICLES
FLUORINE 19
FLUORINE ISOTOPES
GALACTOSE
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HEXOSES
INDOLES
IONS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MEMBRANE PROTEINS
MEMBRANES
MOLECULAR STRUCTURE
MONOSACCHARIDES
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PROTEINS
PYRROLES
RECEPTORS
RESONANCE
SACCHARIDES
STABLE ISOTOPES
TRYPTOPHAN