Atomic-scale structures of surface layers determined by synchrotron diffraction are introduced. Typical X-ray diffraction methods such as surface diffraction and standing waves are summarized. We explain the standard procedure for refining a surface structure model using as an example water molecules adsorbed on a metal crystal surface. We also introduce a hot topic related to the phase problem in surface crystallography: model-independent imaging methods recently developed by several research groups using standing waves and crystal-truncationrod scattering. These methods have enabled atomic-scale visualization of surfaces and interfaces of crystals.
Synchrotron light has brought unprecedented progress in the protein crystallographic studies of macromolecules during the last two decades. The high brilliance and the wavelength tunability are the two key characteristics of the modern synchrotron light sources, but the coordinated effort in providing seamless experimental environments on the experimental stations have proven to be equally important for competitive structural biology research. The advancements did not happen alone but have been made possible by synergy between the synchrotron facilities and users whose high demands kept the former busy in developing new methodologies such as low energy SAD phasing, and other high-throughput techniques. This review summarizes the recent advancements of synchrotron radiation protein crystallography and highlights of structural biology results in the protein transport and posttranslational modification with an overview of what's ahead in the synchrotron light based protein crystallography.
DJ-1 is a multifunctional protein that plays essential roles in organs with higher order biological functions such as testes and brains. DJ-1 is related to male fertility, and its expression level in sperm decreases in response to exposure to sperm toxicants. DJ-1 has also been identified as a hydroperoxide-responsive protein. Recently, a mutation of DJ-1 was found to be responsible for familial Parkinson's disease. Here, we present the crystal structure of DJ-1 refined to 1.95-Å resolution. DJ-1 forms a dimer in the crystal, and the monomer takes a flavodoxin-like Rossmann-fold. DJ-1 monomer is structurally most similar to the monomer subunit of protease I, the intracellular cysteine protease fromPyrococcus horikoshii, and belongs to the Class I glutamine amidotransferase-like superfamily. However, DJ-1 contains an additional a-helix at the C-terminal region, which blocks the putative catalytic site of DJ-1 and appears to regulate the enzymatic activity. DJ-1 may induce conformational changes to acquire catalytic activity in response to oxidative stress.
Emergence of infectious organisms resistant to structurally and functionally dissimilar chemotherapeutic agents is increasingly problematic in human health. This multi-antibiotic resistance is largely caused to the natural or mutational expression of the xenobiotic-antibiotic exporter, which lower the intracellular antibiotic concentration and hence confers the resistance to the bacterium. For better understanding of this important antibiotic transporter, we present the X-ray crystallographic structure of MexA and OprM inPseudomonas aeruginosa. On the basis of the crystal structure of MexA and OprM together with MexB, which was modeled using ACrB, whole MexAB-OprM transporter complex was proposed. And possible mechanism of the OprM gate was discussed.
2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNP), a member of the 2H phosphoesterase superfamily, is found mainly in the central nervous system (CNS) of vertebrates, and it catalyzes the hydrolysis of 2', 3'-cyclic nucleotide to produce 2'-nucleotidein vitro. Recent studies on CNP-knockout mice have revealed that the absence of CNP causes axonal swelling and neuronal degeneration. Here we report crystal structure of the catalytic fragment of human CNP (hCNP-CF) at 1.8Å resolution.