02042naa a2200229 a 450000100080000000500110000800800410001902400360006010000230009624501670011926000090028652012970029565000110159265000140160370000220161770000200163970000160165970000170167570000170169270000200170977300830172920576582016-12-01       2016    bl uuuu     u00u1 u    #d7 a10.1016/j.bbrc.2016.05.0112DOI1 aGIUSEPPE, P. O. de  aA comparative structural analysis reveals distinctive features of cofactor binding and substrate specificity in plant aldo-keto reductases.h[electronic resource]  c2016  aPlant aldo-keto reductases of the AKR4C subfamily play key roles during stress and are attractive targets for developing stress-tolerant crops. However, these AKR4Cs show little to no activity with previouslyenvisioned sugar substrates. We hypothesized a structural basis for the distinctive cofactor binding and substrate specificity of these plant enzymes. To test this, we solved the crystal structure of a novel AKR4C subfamily member, the AKR4C7 from maize, in the apo form and in complex with NADPþ. The binary complex revealed an intermediate state of cofactor binding that preceded closure of Loop B, and also indicated that conformational changes upon substrate binding are required to induce a catalyticallyfavorable conformation of the active-site pocket. Comparative structural analyses of homologues (AKR1B1, AKR4C8 and AKR4C9) showed that evolutionary redesign of plant AKR4Cs weakened interactions that stabilize the closed conformation of Loop B. This in turn decreased cofactor affinity and altered configuration of the substrate-binding site. We propose that these structural modifications contribute to impairment of sugar reductase activity in favor of other substrates in the plant AKR4C subgroup, and that catalysis involves a three-step process relevant to other AKRs.  aEnzima  aReductase1 aSANTOS, M. L. dos1 aSOUSA, S. M. de1 aKOCH, K. E.1 aYUNES, J. A.1 aAPARICIO, R.1 aMURAKAMI, M. T.  tBiochemical and Biophysical Research Communicationsgv. 474, p. 696-701, 2016.