| CueO protein was a predicted bacterial laccase and an appropriate target model for laccase large scale application in industrial production. CueO was also a member of the copper regulatory cue system in Escherichia coli, expressed under conditions of copper stress and showed enhanced oxidase activity when additional copper was present. Four CueO structures were resolved by CueO co crystallized with different concentration copper ion. They revealed the low copper occupation in apo-CueO and a slow copper reconstitution process in each copper site of CueO protein while exogenous copper present. These findings gave us an answer for the copper dependency to CueO oxidase activity. The structural comparison between CueO and other three fungal laccase proteins reminded us 106Glu in CueO was a primary counterwork for trinuclear copper site reconstitution. The mutation of 106Glu observably enhanced CueO copper reconstitution rate and well supported our assumption. We also focused theα-helix from 351Leu to 378Gly would cover substrate biding pocket of CueO and greatly encumber the electron transfer from substrate to type I copper.2-dehydro-3-deoxygalactarate (DDG) aldolase is a member of the class II aldolase family and plays an important role in the pyruvate metabolism pathway, catalyzing the reversible aldol cleavage of DDG to pyruvate and tartronic semialdehyde. As a potential novel antibiotic target, it is necessary to elucidate the catalytic mechanism of DDG aldolase. To determine the crystal structure, crystals of DDG aldolase from Leptospira interrogans were obtained by the hanging-drop vapor-diffusion method. The crystals diffracted to 2.2A resolution on a Cu Kαrotating-anode X-ray source. The crystal belonged to space group C2, with unit-cell parameters a=293.5 A, b=125.6 A, c=87.6 A, andβ=100.9°. The Vm is calculated to be 2.4A~3/Da, when assuming there are twelve protein molecules in the asymmetric unit.
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