Electron spin echo envelope modulation studies of lectins: evidence for a conserved Mn(2+)-binding site.
Electron spin echo envelope modulation (ESEEM) experiments have been used to investigate the Mn(2+)-binding site in a series of lectins including concanavalin A, pea lectin (Pisum sativum), isolectin A from lentil (Lens culinaris), soybean agglutinin (Glycine max), Erythrina indica lectin, and Lotus tetragonolobus isoelectin A. Together with model studies, the results provide direct evidence for a single nitrogen atom of a conserved residue bonded directly to Mn2+ in all of them. ESEEM measurements of the lectins exchanged with deuterium oxide, together with model studies, provide evidence for the presence of two water molecules coordinated to the Mn2+ in all of the proteins. In contrast to concanavalin A, the absence of solvent exchange at the Mn2+ site in the pea and lentil lectins demonstrated by nuclear magnetic relaxation dispersion measurements [Bhattacharyya, L., Brewer, C.F., Brown, R. D., III, & Koenig, S. H. (1985) Biochemistry 24, 4985-4990] must therefore be due to slow exchange of the water ligands of the bound Mn2+. Binding of saccharides was observed to have little effect on the structural features of the Mn2+ site in the lectins as determined by ESEEM.
McCracken
J
J
Department of Molecular Pharmacology, Microbiology and Immunology, Albert Einstein College of medicine, Bronx, New York 10461.
Peisach
J
J
Bhattacharyya
L
L
Brewer
F
F
D001665:Binding Sites; D003903:Deuterium; D017666:Deuterium Oxide; D037102:Lectins / Q000737:chemistry / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008345:Manganese / Q000737:chemistry / Q000378:metabolism*; D009584:Nitrogen; D014867:Water / Q000737:chemistry
D037102:Lectins; D014867:Water; D008345:Manganese; D003903:Deuterium; D017666:Deuterium Oxide; D009584:Nitrogen