Demonstration of a conserved histidine and two water ligands at the Mn2+ site in Diocleinae lectins by pulsed EPR spectroscopy.
Lectins from the Diocleinae subtribe, including Canavalia brasiliensis, Canavalia bonariensis, Canavalia grandiflora, Cratylia floribunda, Dioclea grandiflora, Dioclea guianensis, Dioclea rostrata, Dioclea violacea, and Dioclea virgata, have been recently isolated and characterized in terms of their carbohydrate binding specificities. Although all of the lectins are Man/Glc specific, they possess different biological activities. In the present study, electron paramagnetic resonance (EPR) spectroscopy demonstrates that all nine Diocleinae lectins contain Mn2+. The spectra of C. floribunda and D. rostrata suggest Mn2+ site symmetry different from that of the other seven lectins. However, electron spin-echo envelope modulation (ESEEM) spectroscopy indicates that all nine lectins are coordinated to a histidyl imidazole, with similar electron-nuclear coupling to the Mn2+-bound imidazole nitrogen. ESEEM also demonstrates ligation of two water molecules to Mn2+ in all nine Diocleinae lectins. Thus, the EPR and ESEEM data indicate the presence of a Mn2+ binding site in the above Diocleinae lectins with a conserved histidine residue and two water ligands.
Lee
H C
HC
Departments of Molecular Pharmacology, Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Goroncy
A K
AK
Peisach
J
J
Cavada
B S
BS
Grangeiro
T B
TB
Ramos
M V
MV
Sampaio
A H
AH
Dam
T K
TK
Brewer
C F
CF
D001665:Binding Sites; D002413:Cations, Divalent; D017124:Conserved Sequence; D004578:Electron Spin Resonance Spectroscopy; D007887:Fabaceae; D006639:Histidine / Q000737:chemistry* / Q000378:metabolism; D037102:Lectins / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D008345:Manganese / Q000737:chemistry / Q000378:metabolism*; D037121:Plant Lectins; D010946:Plants, Medicinal; D011485:Protein Binding; D014867:Water / Q000737:chemistry* / Q000378:metabolism
D002413:Cations, Divalent; D037102:Lectins; D008024:Ligands; D037121:Plant Lectins; D014867:Water; D008345:Manganese; D006639:Histidine