1e3j
From Proteopedia
KETOSE REDUCTASE (SORBITOL DEHYDROGENASE) FROM SILVERLEAF WHITEFLY
Overview
Polyhydric alcohols are widely found in nature and can be accumulated to high concentrations as a protection against a variety of environmental stresses. It is only recently, however, that these molecules have been shown to be active in protection against heat stress, specifically in the use of sorbitol by the silverleaf whitefly, Bemisia argentifolii. We have determined the structure of the enzyme responsible for production of sorbitol in Bemisia argentifolii, NADP(H)-dependent ketose reductase (BaKR), to 2.3 A resolution. The structure was solved by multiwavelength anomalous diffraction (MAD) using the anomalous scattering from two zinc atoms bound in the structure, and was refined to an R factor of 21.9 % (R(free)=25.1 %). BaKR belongs to the medium-chain dehydrogenase family and its structure is the first for the sorbitol dehydrogenase branch of this family. The enzyme is tetrameric, with the monomer having a very similar fold to the alcohol dehydrogenases (ADHs). Although the structure determined is for the apo form, a phosphate ion in the active site marks the likely position for the adenyl phosphate of NADP(H). The catalytic zinc ion is tetrahedrally coordinated to Cys41, His66, Glu67 and a water molecule, in a modification of the zinc site usually found in ADHs. This modified zinc site seems likely to be a conserved feature of the sorbitol dehydrogenase sub-family. Comparisons with other members of the ADH family have also enabled us to model a ternary complex of the enzyme, and suggest how structural differences may influence coenzyme binding and substrate specificity in the reduction of fructose to sorbitol.
About this Structure
1E3J is a Single protein structure of sequence from Bemisia argentifolii. Full crystallographic information is available from OCA.
Reference
Crystal structure of the NADP(H)-dependent ketose reductase from Bemisia argentifolii at 2.3 A resolution., Banfield MJ, Salvucci ME, Baker EN, Smith CA, J Mol Biol. 2001 Feb 16;306(2):239-50. PMID:11237597 Page seeded by OCA on Fri May 2 14:37:06 2008
