Understanding Lignin-Degrading Reactions of Ligninolytic Enzymes: Binding Affinity and Interactional Profile

Previous works have demonstrated that ligninolytic enzymes mediated effective degradation of lignin wastes. The degrading ability greatly relied on the interactions of ligninolytic enzymes with lignin. Ligninolytic enzymes mainly contain laccase (Lac), lignin peroxidase (LiP) and manganese peroxidase (MnP). In the present study, the binding modes of lignin to Lac, LiP and MnP were systematically determined, respectively. Robustness of these modes was further verified by molecular dynamics (MD) simulations. Residues GLU460, PRO346 and SER113 in Lac, residues ARG43, ALA180 and ASP183 in LiP and residues ARG42, HIS173 and ARG177 in MnP were most crucial in binding of lignin, respectively. Interactional analyses showed hydrophobic contacts were most abundant, playing an important role in the determination of substrate specificity. This information is an important contribution to the details of enzyme-catalyzed reactions in the process of lignin biodegradation, which can be used as references for designing enzyme mutants with a better lignin-degrading activity

Crystallization and Initial X-Ray Analysis of Rabbit Mature Sterol Carrier Protein 2

Sterol carrier protein 2 (SCP2) is a basic intracellular protein which facilitates the in vitro intermembrane transfer of cholesterol, phospholipids and glycolipids. SCP2 was expressed in Escherichia coli, purified to apparent electrophoretic homogeneity and crystallized. Single crystals were obtained by hanging-drop vapour diffusion using ammonium sulfate as precipitant. These crystals belong to space group P41212 or its enantiomorph, with unit-cell parameters a = b = 57.5, c = 86.5 Å, and have one molecule in the crystallographic asymmetric unit. Intensity data to 1.8 Å resolution were collected from native SCP2 crystals using synchrotron radiation, were processed and scaled with an R(linear) = 4.9%

The crystal structure of SdsA1, an alkylsulfatase from Pseudomonas aeruginosa, defines a third class of sulfatases

Pseudomonas aeruginosa is both a ubiquitous environmental bacterium and an opportunistic human pathogen. A remarkable metabolic versatility allows it to occupy a multitude of ecological niches, including wastewater treatment plants and such hostile environments as the human respiratory tract. P. aeruginosa is able to degrade and metabolize biocidic SDS, the detergent of most commercial personal hygiene products. We identify SdsA1 of P. aeruginosa as a secreted SDS hydrolase that allows the bacterium to use primary sulfates such as SDS as a sole carbon or sulfur source. Homologues of SdsA1 are found in many pathogenic and some nonpathogenic bacteria. The crystal structure of SdsA1 reveals three distinct domains. The N-terminal catalytic domain with a binuclear Zn(2+) cluster is a distinct member of the metallo-β-lactamase fold family, the central dimerization domain ensures resistance to high concentrations of SDS, whereas the C-terminal domain provides a hydrophobic groove, presumably to recruit long aliphatic substrates. Crystal structures of apo-SdsA1 and complexes with substrate analog and products indicate an enzymatic mechanism involving a water molecule indirectly activated by the Zn(2+) cluster. The enzyme SdsA1 thus represents a previously undescribed class of sulfatases that allows P. aeruginosa to survive and thrive under otherwise bacteriocidal conditions