The intrinsically disordered protein TgIST from Toxoplasma gondii inhibits STAT1 signaling by blocking cofactor recruitment

Signal transducer and activator of transcription (STAT) proteins communicate from cell-surface receptors to drive transcription of immune response genes. The parasite Toxoplasma gondii blocks STAT1-mediated gene expression by secreting the intrinsically disordered protein TgIST that traffics to the host nucleus, binds phosphorylated STAT1 dimers, and occupies nascent transcription sites that unexpectedly remain silenced. Here we define a core region within internal repeats of TgIST that is necessary and sufficient to block STAT1-mediated gene expression. Cellular, biochemical, mutational, and structural data demonstrate that the repeat region of TgIST adopts a helical conformation upon binding to STAT1 dimers. The binding interface is defined by a groove formed from two loops in the STAT1 SH2 domains that reorient during dimerization. TgIST binding to this newly exposed site at the STAT1 dimer interface alters its conformation and prevents the recruitment of co-transcriptional activators, thus defining the mechanism of blocked transcription.

Structural basis of SARS-CoV-2 Omicron immune evasion and receptor engagement

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant of concern evades antibody-mediated immunity that comes from vaccination or infection with earlier variants due to accumulation of numerous spike mutations. To understand the Omicron antigenic shift, we determined cryo-electron microscopy and x-ray crystal structures of the spike protein and the receptor-binding domain bound to the broadly neutralizing sarbecovirus monoclonal antibody (mAb) S309 (the parent mAb of sotrovimab) and to the human ACE2 receptor. We provide a blueprint for understanding the marked reduction of binding of other therapeutic mAbs that leads to dampened neutralizing activity. Remodeling of interactions between the Omicron receptor-binding domain and human ACE2 likely explains the enhanced affinity for the host receptor relative to the ancestral virus.

Circulating SARS-CoV-2 spike N439K variants maintain fitness while evading antibody-mediated immunity

SARS-CoV-2 can mutate and evade immunity, with consequences for efficacy of emerging vaccines and antibody therapeutics. Here, we demonstrate that the immunodominant SARS-CoV-2 spike (S) receptor binding motif (RBM) is a highly variable region of S and provide epidemiological, clinical, and molecular characterization of a prevalent, sentinel RBM mutation, N439K. We demonstrate N439K S protein has enhanced binding affinity to the hACE2 receptor, and N439K viruses have similar in vitro replication fitness and cause infections with similar clinical outcomes as compared to wild type. We show the N439K mutation confers resistance against several neutralizing monoclonal antibodies, including one authorized for emergency use by the US Food and Drug Administration (FDA), and reduces the activity of some polyclonal sera from persons recovered from infection. Immune evasion mutations that maintain virulence and fitness such as N439K can emerge within SARS-CoV-2 S, highlighting the need for ongoing molecular surveillance to guide development and usage of vaccines and therapeutics.

Circulating SARS-CoV-2 spike N439K variants maintain fitness while evading antibody-mediated immunity

SARS-CoV-2 can mutate and evade immunity, with consequences for efficacy of emerging vaccines and antibody therapeutics. Here, we demonstrate that the immunodominant SARS-CoV-2 spike (S) receptor binding motif (RBM) is a highly variable region of S and provide epidemiological, clinical, and molecular characterization of a prevalent, sentinel RBM mutation, N439K. We demonstrate N439K S protein has enhanced binding affinity to the hACE2 receptor, and N439K viruses have similar in vitro replication fitness and cause infections with similar clinical outcomes as compared to wild type. We show the N439K mutation confers resistance against several neutralizing monoclonal antibodies, including one authorized for emergency use by the US Food and Drug Administration (FDA), and reduces the activity of some polyclonal sera from persons recovered from infection. Immune evasion mutations that maintain virulence and fitness such as N439K can emerge within SARS-CoV-2 S, highlighting the need for ongoing molecular surveillance to guide development and usage of vaccines and therapeutics.

Cofactor Complexes of DesD, a Model Enzyme in the Virulence-related NIS Synthetase Family

The understudied nonribosomal-peptide-synthetase-independent siderophore (NIS) synthetase family has been increasingly associated with virulence in bacterial species due to its key role in the synthesis of hydroxamate and carboxylate "stealth" siderophores. We have identified a model family member, DesD, from Streptomyces coelicolor, to structurally characterize using a combination of a wild-type and a Arg306Gln variant in apo, cofactor product AMP-bound, and cofactor reactant ATP-bound complexes. The kinetics in the family has been limited by solubility and reporter assays, so we have developed a label-free kinetics assay utilizing a single-injection isothermal-titration-calorimetry-based method. We report second-order rate constants that are 50 times higher than the previous estimations for DesD. Our Arg306Gln DesD variant was also tested under identical buffer and substrate conditions, and its undetectable activity was confirmed. These are the first reported structures for DesD, and they describe the critical cofactor coordination. This is also the first label-free assay to unambiguously determine the kinetics for an NIS synthetase.

The Integration and Use of a Shutterless CMOS Detector at ALS Beamline 4.2.2

The Molecular Biology Consortium Beamline 4.2.2 at the Advanced Light Source has recently installed a new, high-speed, large surface-area CMOS detector for macromolecular crystallography by funds from NIH grant S10OD012073. The detector is 25 x 28 cm and has a readout speed greater than 25 frames per second. This allows shutterless operations and the collection of fine-sliced data. Presented is a description of the hardware and software integration of the detector into the controls system, and the implementation of a streamlined and intuitive collection interface. The interface is implemented in TCL/TK for integration into the beamline's custom Blu-Ice/EPICS environment and remote operations of the beamline with the new detector are routine. The increased sensitivity of the detector and shutterless operations allow for shorter exposure times per image, and up to 3X decrease in time per dataset. Optimum data collection and processing strategies to maximize the benefits of shutterless operations are discussed.

Distinct DNA-binding feature of the peroxide response regulator from group A streptococcus

Group A streptococcus (GAS) is a significant human pathogen, renowned for its rapidly and highly desctructive ability to infect a wide variety of tissues. Clinical manifestation of GAS infection ranges from mild pharyngitis to severe life-threating disease such as necrotizing fasciitis. Unlike other gram-positive bacteria, GAS does not produce catalase, but has an ability to resist killing by reactive oxygen species through unknown novel mechanisms. Our previous studies have discovered that the peroxide response regulator (PerR) is crucial for GAS to cope with oxidative stress and it directly regulates the expression of an iron-binding protein Dpr [1,2]. PerR is a member of Fur (ferric uptake regulator) family which is known to be dimeric, metal-binding regulators. Currently, no structural information is available to understand how the similar structures of the Fur family regulators recognize divergent DNA sequences. To study how PerR interacts with dpr promoter DNA, we have conducted a series of mutagenesis, biochemical and structural studies by combining protein crystallography and small-angle X-ray scattering (SAXS). We have determined the PerR crystal structure to 1.6 Å resolution and identified the DNA-binding residues, which suggest PerR binds to the dpr promoter through a winged-helix motif. By performing SAXS studies, we confirmed that the PerR crystal structure reflects its conformation in solution. Furthermore, SAXS analysis allowed us to resolve the molecular architecture of PerR-DNA complex, in which two 30 bp DNA fragments wrap around two PerR homodimers by interacting with the adjacent positively-charged winged-helix motifs. Our results have revealed the PerR-DNA interaction model and illustrated the DNA-binding mode of PerR that is distinct from all other regulators in Fur family [3].

Tricyclic GyrB/ParE (TriBE) inhibitors: a new class of broad-spectrum dual-targeting antibacterial agents

Increasing resistance to every major class of antibiotics and a dearth of novel classes of antibacterial agents in development pipelines has created a dwindling reservoir of treatment options for serious bacterial infections. The bacterial type IIA topoisomerases, DNA gyrase and topoisomerase IV, are validated antibacterial drug targets with multiple prospective drug binding sites, including the catalytic site targeted by the fluoroquinolone antibiotics. However, growing resistance to fluoroquinolones, frequently mediated by mutations in the drug-binding site, is increasingly limiting the utility of this antibiotic class, prompting the search for other inhibitor classes that target different sites on the topoisomerase complexes. The highly conserved ATP-binding subunits of DNA gyrase (GyrB) and topoisomerase IV (ParE) have long been recognized as excellent candidates for the development of dual-targeting antibacterial agents with broad-spectrum potential. However, to date, no natural product or small molecule inhibitors targeting these sites have succeeded in the clinic, and no inhibitors of these enzymes have yet been reported with broad-spectrum antibacterial activity encompassing the majority of Gram-negative pathogens. Using structure-based drug design (SBDD), we have created a novel dual-targeting pyrimidoindole inhibitor series with exquisite potency against GyrB and ParE enzymes from a broad range of clinically important pathogens. Inhibitors from this series demonstrate potent, broad-spectrum antibacterial activity against Gram-positive and Gram-negative pathogens of clinical importance, including fluoroquinolone resistant and multidrug resistant strains. Lead compounds have been discovered with clinical potential; they are well tolerated in animals, and efficacious in Gram-negative infection models.

Structure of human peptidyl-prolyl cis-trans isomerase FKBP22 containing two EF-hand motifs

The FK506-binding protein (FKBP) family consists of proteins with a variety of protein-protein interaction domains and versatile cellular functions. It is assumed that all members are peptidyl-prolyl cis-trans isomerases with the enzymatic function attributed to the FKBP domain. Six members of this family localize to the mammalian endoplasmic reticulum (ER). Four of them, FKBP22 (encoded by the FKBP14 gene), FKBP23 (FKBP7), FKBP60 (FKBP9), and FKBP65 (FKBP10), are unique among all FKBPs as they contain the EF-hand motifs. Little is known about the biological roles of these proteins, but emerging genetics studies are attracting great interest to the ER resident FKBPs, as mutations in genes encoding FKBP10 and FKBP14 were shown to cause a variety of matrix disorders. Although the structural organization of the FKBP-type domain as well as of the EF-hand motif has been known for a while, it is difficult to conclude how these structures are combined and how it affects the protein functionality. We have determined a unique 1.9 Å resolution crystal structure for human FKBP22, which can serve as a prototype for other EF hand-containing FKBPs. The EF-hand motifs of two FKBP22 molecules form a dimeric complex with an elongated and predominantly hydrophobic cavity that can potentially be occupied by an aliphatic ligand. The FKBP-type domains are separated by a cleft and their putative active sites can catalyze isomerazation of two bonds within a polypeptide chain in extended conformation. These structural results are of prime interest for understanding biological functions of ER resident FKBPs containing EF-hand motifs.

Inelastic X-ray scattering of a transition-metal complex (FeCl4(-)): vibrational spectroscopy for all normal modes

The tetraethylammonium salt of the transition-metal complex FeCl4(-) has been examined using inelastic X-ray scattering (IXS) with 1.5 meV resolution (12 cm(-1)) at 21.747 keV. This sample serves as a feasibility test for more elaborate transition-metal complexes. The IXS spectra were compared with previously recorded IR, Raman, and nuclear resonant vibrational spectroscopy (NRVS) spectra, revealing the same normal modes but with less strict selection rules. Calculations with a previously derived Urey-Bradley force field were used to simulate the expected Q and orientation dependence of the IXS intensities. The relative merits of IXS, compared to other photon-based vibrational spectroscopies such as NRVS, Raman, and IR, are discussed.

Pyrrolopyrimidine inhibitors of DNA gyrase B (GyrB) and topoisomerase IV (ParE). Part I: Structure guided discovery and optimization of dual targeting agents with potent, broad-spectrum enzymatic activity

The bacterial topoisomerases DNA gyrase (GyrB) and topoisomerase IV (ParE) are essential enzymes that control the topological state of DNA during replication. The high degree of conservation in the ATP-binding pockets of these enzymes make them appealing targets for broad-spectrum inhibitor development. A pyrrolopyrimidine scaffold was identified from a pharmacophore-based fragment screen with optimization potential. Structural characterization of inhibitor complexes conducted using selected GyrB/ParE orthologs aided in the identification of important steric, dynamic and compositional differences in the ATP-binding pockets of the targets, enabling the design of highly potent pyrrolopyrimidine inhibitors with broad enzymatic spectrum and dual targeting activity.

Nuclear localization of clathrin involves a labile helix outside the trimerization domain

Clathrin is a trimeric protein involved in receptor-mediated-endocytosis, but can function as a non-trimer outside of endocytosis. We have discovered that the subcellular distribution of a clathrin cysteine mutant we previously studied is altered and a proportion is also localized to nuclear spaces. MALS shows C1573A hub is a mixture of trimer-like and detrimerized molecules. The X-ray structure of the trimerization domain reveals that without light chains, a helix harboring cysteine-1573 is reoriented. We propose clathrin has a detrimerization switch, which suggests clathrin topology can be altered naturally for new functions.

Crystal structures of wild-type and mutated cyclophilin B that causes hyperelastosis cutis in the American quarter horse

Background

Hyperelastosis cutis is an inherited autosomal recessive connective tissue disorder. Affected horses are characterized by hyperextensible skin, scarring, and severe lesions along the back. The disorder is caused by a mutation in cyclophilin B.

Results

The crystal structures of both wild-type and mutated (Gly6->Arg) horse cyclophilin B are presented. The mutation neither affects the overall fold of the enzyme nor impairs the catalytic site structure. Instead, it locally rearranges the flexible N-terminal end of the polypeptide chain and also makes it more rigid.

Conclusions

Interactions of the mutated cyclophilin B with a set of endoplasmic reticulum-resident proteins must be affected.

Structure of MurA (UDP-N-acetylglucosamine enolpyruvyl transferase) from Vibrio fischeri in complex with substrate UDP-N-acetylglucosamine and the drug fosfomycin

The development of new antibiotics is necessitated by the rapid development of resistance to current therapies. UDP-N-acetylglucosamine enolpyruvyl transferase (MurA), which catalyzes the first committed step of bacterial peptidoglycan biosynthesis, is a prime candidate for therapeutic intervention. MurA is the target of the antibiotic fosfomycin, a natural product produced by Streptomyces. Despite possessing a high degree of sequence conservation with MurA enzymes from fosfomycin-susceptible organisms, recent microbiological studies suggest that MurA from Vibrio fischeri (VfiMurA) may confer fosfomycin resistance via a mechanism that is not yet understood. The crystal structure of VfiMurA in a ternary complex with the substrate UDP-N-acetylglucosamine (UNAG) and fosfomycin has been solved to a resolution of 1.93 Å. Fosfomycin is known to inhibit MurA by covalently binding to a highly conserved cysteine in the active site of the enzyme. A comparison of the title structure with the structure of fosfomycin-susceptible Haemophilus influenzae MurA (PDB entry 2rl2) revealed strikingly similar conformations of the mobile substrate-binding loop and clear electron density for a fosfomycin-cysteine adduct. Based on these results, there are no distinguishing sequence/structural features in VfiMurA that would translate to a diminished sensitivity to fosfomycin. However, VfiMurA is a robust crystallizer and shares high sequence identity with many clinically relevant bacterial pathogens. Thus, it would serve as an ideal system for use in the structure-guided optimization of new antibacterial agents.

Crystal structures of progressive Ca2+ binding states of the Ca2+ sensor Ca2+ binding domain 1 (CBD1) from the CALX Na+/Ca2+ exchanger reveal incremental conformational transitions

Na(+)/Ca(2+) exchangers (NCX) constitute a major Ca(2+) export system that facilitates the re-establishment of cytosolic Ca(2+) levels in many tissues. Ca(2+) interactions at its Ca(2+) binding domains (CBD1 and CBD2) are essential for the allosteric regulation of Na(+)/Ca(2+) exchange activity. The structure of the Ca(2+)-bound form of CBD1, the primary Ca(2+) sensor from canine NCX1, but not the Ca(2+)-free form, has been reported, although the molecular mechanism of Ca(2+) regulation remains unclear. Here, we report crystal structures for three distinct Ca(2+) binding states of CBD1 from CALX, a Na(+)/Ca(2+) exchanger found in Drosophila sensory neurons. The fully Ca(2+)-bound CALX-CBD1 structure shows that four Ca(2+) atoms bind at identical Ca(2+) binding sites as those found in NCX1 and that the partial Ca(2+) occupancy and apoform structures exhibit progressive conformational transitions, indicating incremental regulation of CALX exchange by successive Ca(2+) binding at CBD1. The structures also predict that the primary Ca(2+) pair plays the main role in triggering functional conformational changes. Confirming this prediction, mutagenesis of Glu(455), which coordinates the primary Ca(2+) pair, produces dramatic reductions of the regulatory Ca(2+) affinity for exchange current, whereas mutagenesis of Glu(520), which coordinates the secondary Ca(2+) pair, has much smaller effects. Furthermore, our structures indicate that Ca(2+) binding only enhances the stability of the Ca(2+) binding site of CBD1 near the hinge region while the overall structure of CBD1 remains largely unaffected, implying that the Ca(2+) regulatory function of CBD1, and possibly that for the entire NCX family, is mediated through domain interactions between CBD1 and the adjacent CBD2 at this hinge.

Crystal structure of human collagen XVIII trimerization domain: A novel collagen trimerization Fold

Collagens contain a unique triple-helical structure with a repeating sequence -G-X-Y-, where proline and hydroxyproline are major constituents in X and Y positions, respectively. Folding of the collagen triple helix requires trimerization domains. Once trimerized, collagen chains are correctly aligned and the folding of the triple helix proceeds in a zipper-like fashion. Here we report the isolation, characterization, and crystal structure of the trimerization domain of human type XVIII collagen, a member of the multiplexin family. This domain differs from all other known trimerization domains in other collagens and exhibits a high trimerization potential at picomolar concentrations. Strong chain association and high specificity of binding are needed for multiplexins, which are present at very low levels.

Structural evidence for consecutive Hel308-like modules in the spliceosomal ATPase Brr2

Brr2 is a DExD/H-box helicase responsible for U4/U6 unwinding during spliceosomal activation. Brr2 contains two helicase-like domains, each of which is followed by a Sec63 domain with unknown function. We determined the crystal structure of the second Sec63 domain, which unexpectedly resembles domains 4 and 5 of DNA helicase Hel308. This, together with sequence similarities between Brr2’s helicase-like domains and domains 1–3 of Hel308, led us to hypothesize that Brr2 contains two consecutive Hel308-like modules (Hel308-I and II). Our structural model and mutagenesis data suggest that Brr2 shares a similar helicase mechanism with Hel308. We demonstrate that Hel308-II interacts with Prp8 and Snu114 in vitro and in vivo. We further find that the C-terminal region of Prp8 (Prp8-CTR) facilitates the binding of the Brr2/Prp8-CTR complex to U4/U6. Our results have important implications for the mechanism and regulation of Brr2’s activity.

Search for a light pseudoscalar particle in the decay K_{L};{0}-->pi;{0}pi;{0}X

We performed a search for a light pseudoscalar particle X in the decay K_{L};{0}-->pi;{0}pi;{0}X, X-->gammagamma with the E391a detector at KEK. Such a particle with a mass of 214.3 MeV/c;{2} was suggested by the HyperCP experiment. We found no evidence for X and set an upper limit on the product branching ratio for K_{L};{0}-->pi;{0}pi;{0}X, X-->gammagamma of 2.4x10;{-7} at the 90% confidence level. Upper limits on the branching ratios in the mass region of X from 194.3 to 219.3 MeV/c;{2} are also presented.

Structures of the rare-cutting restriction endonuclease NotI reveal a unique metal binding fold involved in DNA binding

The structure of the rare-cutting restriction endonuclease NotI, which recognizes the 8 bp target 5'-GCGGCCGC-3', has been solved with and without bound DNA. Because of its specificity (recognizing a site that occurs once per 65 kb), NotI is used to generate large genomic fragments and to map DNA methylation status. NotI contains a unique metal binding fold, found in a variety of putative endonucleases, occupied by an iron atom coordinated within a tetrahedral Cys4 motif. This domain positions nearby protein elements for DNA recognition, and serves a structural role. While recognition of the central six base pairs of the target is accomplished via a saturated hydrogen bond network typical of restriction enzymes, the most peripheral base pairs are engaged in a single direct contact in the major groove, reflecting reduced pressure to recognize those positions. NotI may represent an evolutionary intermediate between mobile endonucleases (which recognize longer target sites) and canonical restriction endonucleases.

Search for the Decay K L0-->pi0nu nu[over]

We performed a search for the K L0-->pi0nu nu[over] decay at the KEK 12-GeV proton synchrotron. No candidate events were observed. An upper limit on the branching ratio for the decay was set to be 6.7 x 10(-8) at the 90% confidence level.

Crystal structure at 2.8 A of the DLLRKN-containing coiled-coil domain of huntingtin-interacting protein 1 (HIP1) reveals a surface suitable for clathrin light chain binding

Huntingtin interacting protein 1 (HIP1) is a member of a family of proteins whose interaction with Huntingtin is critical to prevent cells from initiating apoptosis. HIP1, and related protein HIP12/1R, can also bind to clathrin and membrane phospholipids, and HIP12/1R links the CCV to the actin cytoskeleton. HIP1 and HIP12/1R interact with the clathrin light chain EED regulatory site and stimulate clathrin lattice assembly. Here, we report the X-ray structure of the coiled-coil domain of HIP1 (residues 482-586) that includes residues crucial for binding clathrin light chain. The dimeric HIP1 crystal structure is partially splayed open. The comparison of the HIP1 model with coiled-coil predictions revealed the heptad repeat in the dimeric trunk (S2 path) is offset relative to the register of the heptad repeat from the N-terminal portion (S1 path) of the molecule. Furthermore, surface analysis showed there is a third hydrophobic path (S3) running parallel with S1 and S2. We present structural evidence supporting a role for the S3 path as an interaction surface for clathrin light chain. Finally, comparative analysis suggests the mode of binding between sla2p and clathrin light chain may be different in yeast.

Structural basis for the inhibition of Aurora A kinase by a novel class of high affinity disubstituted pyrimidine inhibitors

The 2.25 A crystal structure of a complex of Aurora A kinase (AIKA) with cyclopropanecarboxylic acid-(3-(4-(3-trifluoromethyl-phenylamino)-pyrimidin-2-ylamino)-phenyl)-amide 1 is described here. The inhibitor binding mode is novel, with the cyclopropanecarboxylic acid moiety directed towards the solvent exposed region of the ATP-binding pocket, and several induced structural changes in the active-site compared with other published AIK structures. This structure provides context for the available SAR data on this compound class, and could be exploited for the design of analogs with increased affinity and selectivity for AIK.

The 1.3 A crystal structure of a biotin-binding pseudoknot and the basis for RNA molecular recognition

A pseudoknot-containing aptamer isolated from a pool of random sequence molecules has been shown previously to represent an optimal RNA solution to the problem of binding biotin. The affinity of this RNA molecule is nonetheless orders of magnitude weaker than that of its highly evolved protein analogs, avidin and streptavidin. To understand the structural basis for biotin binding and to compare directly strategies for ligand recognition available to proteins and RNA molecules, we have determined the 1.3 A crystal structure of the aptamer complexed with its ligand. Biotin is bound at the interface between the pseudoknot's stacked helices in a pocket defined almost entirely by base-paired nucleotides. In comparison to the protein avidin, the aptamer packs more tightly around the biotin headgroup and makes fewer contacts with its fatty acid tail. Whereas biotin is deeply buried within the hydrophobic core in the avidin complex, the aptamer relies on a combination of hydrated magnesium ions and immobilized water molecules to surround its ligand. In addition to demonstrating fundamentally different approaches to molecular recognition by proteins and RNA, the structure provides general insight into the mechanisms by which RNA function is mediated by divalent metals.

Functional requirements for specific ligand recognition by a biotin-binding RNA pseudoknot

Ligand-binding RNAs and DNAs (aptamers) isolated by in vitro selection from random sequence pools provide convenient model systems for understanding the basic relationships between RNA structure and function. We describe a series of experiments that define the functional requirements for an RNA motif that specifies high-affinity binding to the carboxylation cofactor biotin. A simple pseudoknot containing an adenosine-rich loop accounts for binding in all independently derived aptamers selected to bind biotin, suggesting that it alone represents a global optimum for recognition of this particular nonaromatic, electrostatically neutral ligand. In contrast to virtually all previously identified aptamers, unpaired nucleotides make up a small fraction of the binding motif. Instead, the identity of 14 nucleotides involved in base pairing is highly conserved among functional clones and their substitution by nonidentical base pairs significantly reduces or eliminates binding. Chemical probing is consistent with the predicted pseudoknot motif and indicates that relatively little change in structure accompanies ligand binding, a strong contrast with results for other aptamers. Competition experiments suggest that the aptamer recognizes all parts of the biotin ligand, including its thiophane ring and fatty acid tail. Two alternative modes of binding are suggested by a three-dimensional model of the pseudoknot, both of which entail significant interactions with base-paired nucleotides.

Expression of hepatic metallothionein messenger RNA in feral and caged fish species correlates with muscle mercury levels

Metallothioneins (MTs) are low-molecular-weight cytosolic proteins that are induced by cellular stress as well as exposure to various heavy metals including mercury. Excessive residues of mercury have recently been identified in various fish species of the lower Ouachita River system in Arkansas. Fillets of mature largemouth bass (Micropterus salmoides) collected from Woodard Lake, an ox-bow lake of the Ouachita River, possessed muscle residues of mercury ranging from 0.3 to 1.0 ppm (micrograms/g). To assess the usefulness of using MT expression as a biomarker of mercury exposure, livers and fillets were obtained from feral bass of Woodard Lake. Ouachita served as a control site having mercury residues below detection. Analyses using a ribonuclease protection assay with winter flounder MT cDNA revealed that bass had significantly elevated levels of MT mRNA which correlated (r2 = 0.756) with the levels of mercury in muscle fillets. To further explore the water quality of Woodard Lake, 10 juvenile channel catfish were housed in cages and placed where feral collections were made in both sites for 2 weeks. Mercury was not detected in muscle or liver and no significant difference in hepatic MT mRNA was observed. These data demonstrate that MT mRNA expression can be used as a tool to assess exposure to heavy metals and suggest that the elevated levels of mercury in large predatory fish may be due to trophic magnification rather than a single point-source exposure.

Mapping of the trifunctional fatty acid synthetase gene FAS2 on chromosome XVI of Saccharomyces cerevisiae

The trifunctional FAS2 gene encoding subunit alpha of the Saccharomyces cerevisiae fatty acid synthetase complex was mapped on the left arm of chromosome XVI 24 centimorgans proximal to GAL4 and 39 centimorgans distal to PEP4 relative to the centromere. Mapping was achieved by three independent methods: meiotic co-segregation of FAS2 and ARO7 in recombination-deficient spo11-mutants: tetrad analysis of crosses between FAS2, GAL4 and PEP4; and Southern hybridization of purified FAS2 DNA with individual yeast chromosomes separated by pulsed-field gel electrophoresis.

Short-term nursing therapy: a conceptual model for inpatient psychiatric care

As a result of changing perspectives in psychiatric practice and increasing fiscal limits imposed by legislative and economic issues, psychiatric nurses have found their traditional models of practice challenged by shortened lengths of stay and the need for more efficient assessment and treatment. Short-term nursing therapy, which draws on the principles of crisis intervention and brief psychotherapy, was developed to provide psychiatric nurses with a cohesive, comprehensive nursing philosophy for practical application in changing inpatient settings. The authors review the development of the short-term nursing therapy concept from the perspective of the changing inpatient milieu and nurse-patient relationship. They then discuss the assumptions that constitute its framework, as well as other key factors in its implementation.

Reproductive performance and profitability of heifers fed to weigh 272 or 318 kg at the start of the first breeding season

Reproductive performance and weaning weight of the first calf was determined in 221 Brahman crossbred heifers fed to weigh either 272 (TW1) or 318 kg (TW2) at the start of their first breeding season (target weight). Heifers were divided into light- (below average) and heavyweight (above average) groups on the basis of initial weight. Within each target weight, heifers were fed in three lots. One lot contained lightweight heifers, the second contained heavy heifers and the third was composed of one-half heavy- and one-half lightweight heifers. Heifers were fed for 200 d before the start of the first breeding season. More heifers in TW2 showed estrus and became pregnant in the first 20 d of the breeding season and more were pregnant at the end of the first breeding season. These same differences in reproductive performance were also noted the second year. Each heifer exposed in TW2 weaned 43.4 kg more calf than those in TW1. An average heifer in TW2 was fed 220 kg more corn and 100 kg less hay than a corresponding heifer in TW1. Estrus and pregnancy rate for lightweight heifers in TW1 and TW2 were not improved by sorting and feeding them separately.

Relationship between sex, sex-role characteristics and coronary-prone behavior in college students

Coronary-prone behavior is most prevalent in middle-age males. The incidence of coronary-prone behavior has been attributed to employment patterns in which male sex-role characteristics of achievement are encouraged. A relationship between coronary-prone behavior and sex-role orientation is thus implied. The present study was undertaken to determine the nature of the relationship. Multiple-regression analyses showed the greatest proportion of coronary-prone behavior is accounted for by masculine sex-role characteristics. The results support the hypothesis that coronary-prone behavior is a male sex-role characteristic. The common influences of sex-role socialization practices upon masculine and feminine characteristics and upon coronary-prone behavior are discussed.