Isolated eyelid neonatal Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) is a condition characterized by clonal proliferation of the phagocytic cells derived from the bone marrow. In this article, we present an exceedingly rare case of congenital/neonatal LCH in a 3-week-old girl who initially presented with an isolated swelling of the eyelid, initially misdiagnosed as a chalazion. Subsequently, a biopsy was performed, and histopathological evaluation confirmed the diagnosis of LCH.

Discovery, Design, and Structural Characterization of Alkane-Producing Enzymes across the Ferritin-like Superfamily.

To complement established rational and evolutionary protein design approaches, significant efforts are being made to utilize computational modeling and the diversity of naturally occurring protein sequences. Here, we combine structural biology, genomic mining, and computational modeling to identify structural features critical to aldehyde deformylating oxygenases (ADOs), an enzyme family that has significant implications in synthetic biology and chemoenzymatic synthesis. Through these efforts, we discovered latent ADO-like function across the ferritin-like superfamily in various species of Bacteria and Archaea.

Dopamine maintains network synchrony via direct modulation of gap junctions in the crustacean cardiac ganglion.

The Large Cell (LC) motor neurons of the crab cardiac ganglion have variable membrane conductance magnitudes even within the same individual, yet produce identical synchronized activity in the intact network. In a previous study we blocked a subset of K conductances across LCs, resulting in loss of synchronous activity (Lane et al., 2016).

Structure and specificity of several triclocarban-binding single domain camelid antibody fragments.

The variable VHH domains of camelid single chain antibodies have been useful in numerous biotechnology applications due to their simplicity, biophysical properties, and abilities to bind to their cognate antigens with high affinities and specificity. Their interactions with proteins have been well-studied, but considerably less work has been done to characterize their ability to bind haptens. A high-resolution structural study of three nanobodies (T4, T9, and T10) which have been shown to bind triclocarban (TCC, 3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea) with near-nanomolar affinity shows that binding occurs in a tunnel largely formed by CDR1 rather than a surface or lateral binding mode seen in other nanobody-hapten interactions.

Conformational flexibility related to enzyme activity: evidence for a dynamic active-site gatekeeper function of Tyr(215) in Aerococcus viridans lactate oxidase.

L-Lactate oxidase (LOX) belongs to a large family of flavoenzymes that catalyze oxidation of α-hydroxy acids. How in these enzymes the protein structure controls reactivity presents an important but elusive problem. LOX contains a prominent tyrosine in the substrate binding pocket (Tyr(215) in Aerococcus viridans LOX) that is partially responsible for securing a flexible loop which sequesters the active site.

Speeding up the product release: a second-sphere contribution from Tyr191 to the reactivity of L-lactate oxidase revealed in crystallographic and kinetic studies of site-directed variants.

Among α-hydroxy acid-oxidizing flavoenzymes l-lactate oxidase (LOX) is unique in featuring a second-sphere tyrosine (Tyr191 in Aerococcus viridans LOX; avLOX) at the binding site for the substrate's carboxylate group. Y191F, Y191L and Y191A variants of avLOX were constructed to affect a hydrogen-bond network connecting Tyr191 to the carboxylate of the bound ligand via the conserved Tyr40 and to examine consequent effects on enzymatic reactivity. Kinetic studies at 20 °C and pH 6.

The Ala95-to-Gly substitution in Aerococcus viridans l-lactate oxidase revisited - structural consequences at the catalytic site and effect on reactivity with O2 and other electron acceptors.

Aerococcus viridansl-lactate oxidase (avLOX) is a biotechnologically important flavoenzyme that catalyzes the conversion of L-lactate and O₂ into pyruvate and H₂O₂. The enzymatic reaction underlies different biosensor applications of avLOX for blood L-lactate determination. The ability of avLOX to replace O₂ with other electron acceptors such as 2,6-dichlorophenol-indophenol (DCIP) allows the possiblity of analytical and practical applications.

Identification, characterization, and crystal structure of an aldo-keto reductase (AKR2E4) from the silkworm Bombyx mori.

A new member of the aldo-keto reductase (AKR) superfamily with 3-dehydroecdysone reductase activity was found in the silkworm Bombyx mori upon induction by the insecticide diazinon. The amino acid sequence showed that this enzyme belongs to the AKR2 family, and the protein was assigned the systematic name AKR2E4. In this study, recombinant AKR2E4 was expressed, purified to near homogeneity, and kinetically characterized.

Crystallographic observation of pH-induced conformational changes in the Amyelois transitella pheromone-binding protein AtraPBP1.

The navel orangeworm, Amyelois transitella is a major agricultural pest causing large losses in a variety of tree crops. Control of this insect pest may be achieved by interfering with olfactory pathways to block detection of female-produced sex pheromones and consequently, disrupt mating. The first component of this pathway is the pheromone-binding protein AtraPBP1, which recognizes the pheromone and presents it to the odorant receptor housed in a sensory neuron of the male antennae.

Function of phenylalanine 259 and threonine 314 within the substrate binding pocket of the juvenile hormone esterase of Manduca sexta.

Juvenile hormone (JH) is a key insect developmental hormone that is found at low nanomolar levels in larval insects. The methyl ester of JH is hydrolyzed in many insects by an esterase that shows high specificity for JH. We have previously determined a crystal structure of the JH esterase (JHE) of the tobacco hornworm Manduca sexta (MsJHE) [Wogulis, M.

Comprehensive X-ray structural studies of the quinolinate phosphoribosyl transferase (BNA6) from Saccharomyces cerevisiae.

Quinolinic acid phosphoribosyl transferase (QAPRTase, EC 2.4.2.

Identification of formyl kynurenine formamidase and kynurenine aminotransferase from Saccharomyces cerevisiae using crystallographic, bioinformatic and biochemical evidence.

The essential enzymatic cofactor NAD+ can be synthesized in many eukaryotes, including Saccharomyces cerevisiae and mammals, using tryptophan as a starting material. Metabolites along the pathway or on branches have important biological functions. For example, kynurenic acid can act as an NMDA antagonist, thereby functioning as a neuroprotectant in a wide range of pathological states.

Structural and kinetic studies of induced fit in xylulose kinase from Escherichia coli.

The primary metabolic route for D-xylose, the second most abundant sugar in nature, is via the pentose phosphate pathway after a two-step or three-step conversion to xylulose-5-phosphate. Xylulose kinase (XK; EC 2.7.

Catalytic mechanism and substrate selectivity of aldo-keto reductases: insights from structure-function studies of Candida tenuis xylose reductase.

Aldo-keto reductases (AKRs) constitute a large protein superfamily of mainly NAD(P)-dependent oxidoreductases involved in carbonyl metabolism. Catalysis is promoted by a conserved tetrad of active site residues (Tyr, Lys, Asp and His). Recent results of structure-function relationship studies for xylose reductase (AKR2B5) require an update of the proposed catalytic mechanism.

On-bead combinatorial techniques for the identification of selective aldose reductase inhibitors.

Aldose reductase (AKR1B1; ALR2; E.C. 1.

Identification of a novel NADH-specific aldo-keto reductase using sequence and structural homologies.

The AKRs (aldo-keto reductases) are a superfamily of enzymes which mainly rely on NADPH to reversibly reduce various carbonyl-containing compounds to the corresponding alcohols. A small number have been found with dual NADPH/NADH specificity, usually preferring NADPH, but none are exclusive for NADH. Crystal structures of the dual-specificity enzyme xylose reductase (AKR2B5) indicate that NAD+ is bound via a key interaction with a glutamate that is able to change conformations to accommodate the 2'-phosphate of NADP+.

Structural studies of a potent insect maturation inhibitor bound to the juvenile hormone esterase of Manduca sexta.

Juvenile hormone (JH) is an insect hormone containing an alpha,beta-unsaturated ester consisting of a small alcohol and long, hydrophobic acid. JH degradation is required for proper insect development. One pathway of this degradation is through juvenile hormone esterase (JHE), which cleaves the JH ester bond to produce methanol and JH acid.

Structure-guided engineering of xylitol dehydrogenase cosubstrate specificity.

Xylitol dehydrogenase (XDH) is one of several enzymes responsible for assimilating xylose into eukaryotic metabolism and is useful for fermentation of xylose contained in agricultural byproducts to produce ethanol. For efficient xylose utilization at high flux rates, cosubstrates should be recycled between the NAD+-specific XDH and the NADPH-preferring xylose reductase, another enzyme in the pathway. To understand and alter the cosubstrate specificity of XDH, we determined the crystal structure of the Gluconobacter oxydans holoenzyme to 1.

Probing the substrate binding site of Candida tenuis xylose reductase (AKR2B5) with site-directed mutagenesis.

Little is known about how substrates bind to CtXR (Candida tenuis xylose reductase; AKR2B5) and other members of the AKR (aldo-keto reductase) protein superfamily. Modelling of xylose into the active site of CtXR suggested that Trp23, Asp50 and Asn309 are the main components of pentose-specific substrate-binding recognition. Kinetic consequences of site-directed substitutions of these residues are reported.

The crystal structure of an odorant binding protein from Anopheles gambiae: evidence for a common ligand release mechanism.

The Anopheles gambiae mosquito is the main vector of malaria transmission in sub-Saharan Africa. We present here a 1.5A crystal structure of AgamOBP1, an odorant binding protein (OBP) from the A.

The structure of Sif2p, a WD repeat protein functioning in the SET3 corepressor complex.

In Saccharomyces cerevisiae, the SIF2 gene product is an integral component of the Set3 complex (SET3C), an assembly of proteins with some homology to the human SMRT and N-CoR corepressor complexes. SET3C has histone deacetylase activity that is responsible for repressing a set of meiotic genes. We have determined the X-ray crystal structure of a 46 kDa C-terminal domain of a SET3C core protein, Sif2p to 1.

Discovery of selective aldo-keto reductase ligands--an on-bead assay strategy.

An enzyme labeling and screening strategy for the discovery of ligands selective in binding two structurally similar members of the aldo-keto reductase family of enzymes is reported. The resulting fluorescence microscope data obtained by screening a 74,088 member library led to the identification of selective ligands for aldose reductase (ALR2) and aldehyde reductase (ALR1). Resynthesis results validate the selectivity of these ligands.

Fine tuning of coenzyme specificity in family 2 aldo-keto reductases revealed by crystal structures of the Lys-274-->Arg mutant of Candida tenuis xylose reductase (AKR2B5) bound to NAD+ and NADP+.

Aldo-keto reductases of family 2 employ single site replacement Lys-->Arg to switch their cosubstrate preference from NADPH to NADH. X-ray crystal structures of Lys-274-->Arg mutant of Candida tenuis xylose reductase (AKR2B5) bound to NAD+ and NADP+ were determined at a resolution of 2.4 and 2.

The 1.1-angstrom structure of the spindle checkpoint protein Bub3p reveals functional regions.

Bub3p is a protein that mediates the spindle checkpoint, a signaling pathway that ensures correct chromosome segregation in organisms ranging from yeast to mammals. It is known to function by co-localizing at least two other proteins, Mad3p and the protein kinase Bub1p, to the kinetochore of chromosomes that are not properly attached to mitotic spindles, ultimately resulting in cell cycle arrest. Prior sequence analysis suggested that Bub3p was composed of three or four WD repeats (also known as WD40 and beta-transducin repeats), short sequence motifs appearing in clusters of 4-16 found in many hundreds of eukaryotic proteins that fold into four-stranded blade-like sheets.

The coenzyme specificity of Candida tenuis xylose reductase (AKR2B5) explored by site-directed mutagenesis and X-ray crystallography.

CtXR (xylose reductase from the yeast Candida tenuis; AKR2B5) can utilize NADPH or NADH as co-substrate for the reduction of D-xylose into xylitol, NADPH being preferred approx. 33-fold. X-ray structures of CtXR bound to NADP+ and NAD+ have revealed two different protein conformations capable of accommodating the presence or absence of the coenzyme 2'-phosphate group.