The dimer contact area of sorghum NADP-malate dehydrogenase: role of aspartate 101 in dimer stability and catalytic activity

During thioredoxin-mediated activation of chloroplastic NADP-malate dehydro genase, a homodimeric enzyme, the interaction between subunits is known to be loosened but maintained, A modeling of the 3D structure of the protein i dentified Asp-101 as being potentially involved in the association between subunits through an electrostatic interaction. Indeed, upon site-directed s ubstitution of Asp-101 by an asparagine, the mutated enzyme behaved mainly as a monomer, The mutation strongly affected the catalytical efficiency of the enzyme. The non available 3D structure of the enzyme shows that Asp-101 is protruding at the dimer interface, interacting with Arg-268 of the neig hbouring subunit, (C) 2000 Federation of European Biochemical Societies.