Individual and geographical variation in display behaviour of male harbour seals in Scotland

Studying variations in behaviour at the individual or population level enables insight into the reproductive strategies within a species. We examined individual and geographical variation in the vocal and dive behaviour of male harbour seals, Phoca vitulina, which is associated with aquatic mating. This display behaviour was recorded in the Moray Firth, Scotland, from July 1994 to 1997, and in Orkney, Scotland, during July 1998. One vocalization type was apparent in the Moray Firth and two in Orkney. Time parameters (total and pulse duration) varied between males in the population in the Moray Firth. We used both frequency and time parameters in a discriminant analysis, which showed that 73.2% of individual male vocalizations could be correctly classified; 94.6% of male vocalizations from the Moray Firth and Orkney could be correctly classified according to their geographical areas. Therefore, vocal variation was greater between geographical areas than between individuals. No individual variation was apparent between dive and surface interval durations. However, individuals varied significantly in the percentage of short surface intervals. Male harbour seals showed substantial variability in the parameters affecting their vocal and dive behaviour during the mating season. We suggest that these variations may be indicative of adaptations to varying environmental challenges influencing the reproductive strategies of discrete populations. Copyright 2000 The Association for the Study of Animal Behaviour.     

Ligand binding and allostery can emerge simultaneously

A heterotropic allosteric effect involves an effector molecule that is distinct from the substrate or ligand of the protein. How heterotropic allostery originates is an unanswered question. We have previously created several heterotropic allosteric enzymes by recombining the genes for TEM1 beta-lactamase (BLA) and maltose binding protein (MBP) to create BLAs that are positively or negatively regulated by maltose. We show here that one of these engineered enzymes has approximately 10(6) M(-1) affinity for Zn(2+), a property that neither of the parental proteins possesses. Furthermore, Zn(2+) is a negative effector that noncompetitively switches off beta-lactam hydrolysis activity. Mutagenesis experiments indicate that the Zn(2+)-binding site does not involve a histidine or a cysteine, which is atypical of natural Zn(2+)-binding sites. These studies also implicate helices 1 and 12 of the BLA domain in allosteric signal propagation. These results support a model for the evolution of heterotropic allostery in which effector affinity and allosteric signaling emerge simultaneously.     

Rheumatoid peripheral blood phagocytes are primed for activation but have impaired Fc-mediated generation of reactive oxygen species

Significant levels of circulating immune complexes (ICs) containing rheumatoid factors and immunoglobulin G in peripheral blood are a characteristic feature of rheumatoid arthritis (RA). ICs interact through Fcγ receptors (FcγR) to activate phagocytes in numerous inflammatory processes. The high concentration of neutrophils in synovial fluid during active phases of the disease, together with their destructive capacity, pose important questions as to their role in the pathogenesis of RA. Functional defects in RA or control peripheral blood neutrophil FcγRs were examined with a specific FcγR-mediated reactive oxygen species (ROS) assay. Heterologous cross-linking of FcγRIIa and FcγRIIIb on neutrophils resulted in a significantly decreased production of ROS by RA cells compared with controls matched for age and sex. However, expression and homologous ligation of receptors did not differ between these groups. These data suggest that neutrophil priming does occur before emigration into the joint and that blood neutrophils from patients with RA have a functional impairment in cooperative FcγR-mediated ROS generation. This may account for the increased susceptibility to bacterial infection that arises in patients with severe disease.     

Advancements in the Development of HIF-1α-Activated Protein Switches for Use in Enzyme Prodrug Therapy

While gene-directed enzyme prodrug therapy has shown potential as a cancer therapeutic in animal and clinical trials, concerns over the efficacy, selectivity, and safety of gene delivery vehicles have restricted its advance. In an attempt to relieve some of the demands on targeted gene delivery vehicles and achieve the full potential of enzyme prodrug therapy, cancer-targeted activity can be engineered into the enzyme itself. We previously engineered a switchable prodrug-activating enzyme that selectively kills human cancer cells accumulating the cancer marker hypoxia-inducible factor-1α (HIF-1α). This HIF-1α-activated protein switch (Haps59) is designed to increase its ability to convert the prodrug 5-fluorocytosine into the chemotherapeutic 5-fluorouracil in a HIF-1α-dependent manner. However, in cancer cell lines expressing Haps59 the 5FC sensitivity difference between the presence and absence of HIF-1α was not as large as desired. In this work, we aimed to improve the cancer specificity of this switch via a directed evolution approach utilizing random mutagenesis, linker mutagenesis, and random insertion and circular permutation. We identified improved HIF-1α-activated protein switches that confer E. coli with modest increases in HIF-1α-dependent 5FC toxicity. Additionally, the current bottleneck in the development of improved HIF-1α-activated protein switches is screening switch candidates in mammalian cells. To accommodate higher throughput and reduce experimental variability, we explored the use of Flp recombinase-mediated isogenic integration in 293 cells. These experiments raised the possibility that Haps59 can be activated by other interactors of the CH1 domain, and experiments in E. coli indicated that CITED2 can also activate Haps59. Although many CH1 binding partners are also oncogenes, CH1''s promiscuous binding and subsequent off-target activation of Haps59 needs to be examined under normal physiological conditions to identify off-target activators. With aberrant activating molecules identified, further directed evolution can be performed to improve the cancer specificity of HIF-1α-activated protein switches.     

CD14 C-159T and early infection with Pseudomonas aeruginosa in children with cystic fibrosis

Early acquisition of Pseudomonas aeruginosa is associated with a poorer prognosis in patients with cystic fibrosis. We investigated whether polymorphisms in CD14, the lipopolysaccharide receptor, increase the risk of early infection. Forty-five children with cystic fibrosis were investigated with annual bronchoalveolar lavage (BAL) and plasma sCD14 levels. Plasma sCD14 levels were significantly lower in children from whom P.aeruginosa was subsequently isolated (492.75 μg/ml vs. 1339.43 μg/ml, p = 0.018). Those with the CD14 -159CC genotype had a significantly increased risk of early infection with P.aeruginosa suggesting that CD14 C-159T plays a role in determining the risk of early infection with P.aeruginosa.     

降解烤烟秸秆和烟碱菌株的筛选及其产酶特性

摘要:【目的】为获得能够降解烤烟秸秆和烟碱的菌株,并探索其降解烤烟秸秆的利用途径。【方法】以烤烟秸秆为唯一碳氮源,从烟田土壤中进行了菌株的筛选。采用形态学观察、生理生化特性鉴定、16S rRNA基因序列鉴定等方法对该菌株进行了鉴定,并对其以烤烟秸秆为底物进行液态发酵的产酶活性和木质纤维素降解效果进行了测定。【结果】结果表明:该菌株为巨大芽孢杆菌(Bacillus megaterium)。在以烤烟秸秆为主要营养物质液态发酵条件下该菌株具有较强的木质素降解能力,最大漆酶活力达到418.52 U/L,而木质素过氧化物酶和锰过氧化物酶的最大酶活分别为19.71 U/L 和64.71 U/L。此外,发酵20 d后该菌能够完全降解发酵液中的烟碱。【结论】本研究筛选到了1株能够较好降解烤烟秸秆和完全降解烟碱的巨大芽孢杆菌(Bacillus megaterium),且该菌株具有利用烤烟秸秆生产漆酶的应用价值。     

Circular permutation in the Ω-loop of TEM-1 β-lactamase results in improved activity and altered substrate specificity

Generating diverse protein libraries that contain improved variants at a sufficiently high frequency is critical for improving the properties of proteins using directed evolution. Many studies have illustrated how random mutagenesis, cassette mutagenesis, DNA shuffling and similar approaches are effective diversity generating methods for directed evolution. Very few studies have explored random circular permutation, the intramolecular relocation of the N- and C-termini of a protein, as a diversity-generating step for directed evolution. We subjected a library of random circular permutations of TEM-1 β-lactamase to selections on increasing concentrations of a variety of β-lactam antibiotics including cefotaxime. We identified two circularly permuted variants that conferred elevated resistance to cefotaxime but decreased resistance to other antibiotics. These variants were circularly permuted in the Ω-loop proximal to the active site. Remarkably, one variant was circularly permuted such that the key catalytic residue Glu166 was located at the N-terminus of the mature protein.