The 300-kDa intermediate filament-associated protein (IFAP300) is a hamster plectin ortholog

Plectin is a high-molecular-weight cytoskeleton-associated protein that was initially identified in intermediate filament (IF)-enriched fractions of rat C6 glioma cells. At the cellular level, plectin has been found to associate with IF networks and IF-associated structures that are involved in cell-cell and cell-substrate adhesions. IFAP300 is an IF-associated protein that was initially identified in hamster cells by a monoclonal antibody directed against a high molecular weight protein present in IF-enriched cytoskeletal preparations. Plectin and IFAP300 display similar distribution patterns within cells as determined by immunofluorescence. Based upon this and the finding that their biochemical properties are similar, it has been suggested that they may actually be orthologous proteins. In this paper we demonstrate that this is the case. Cloning and sequencing of most of the hamster plectin cDNA demonstrates that plectin is found in hamster cells and that its sequence is highly conserved between species. Using immunological cross-reactivity, epitope mapping, and immunoelectron microscopy, we show that IFAP300 is actually the hamster ortholog of plectin.     

补增UV—B辐射对香蕉叶片光合作用和叶氮在光合碳循环组分中分配 …

补增UV -B辐射的香蕉叶片光下呼吸速率 (Rd)和不包括光下呼吸的CO2 补偿点 (г ) ,分别为0 .33μmol·m- 2 ·s- 1 和 46.5μl·L- 1 ,较对照植株分别高 5.6%和 1 0 .0 %。在较高CO2 浓度 (>340 μl·L- 1 )条件下的An/θp关系最初直线部分斜率 ,即表观量子产率 (αA)为 0 .0 2 3± 0 .0 0 7,而补增UV B辐射处理的植株则降低 1 3.0 % ,光能转换效率 (δ)亦降低 2 8.6% ,表明UV B辐射明显降低αA 和δ。在高θp(1 1 0 0 μmol·m- 2 ·s- 1 )和Ci<2 0 0 μl·L- 1 条件下 ,对照植株的An/Ci关系为An =0 .0 2 8Ci 1 .44,补增UV B辐射处理的植株则为An =0 .0 2 1Ci 1 .0 1 ,UV B辐射降低羧化限制速率。最大羧化速率 (Vcmax)和电子传导速率的光饱和值 (Jmax)亦较低 ,补增UV B辐射的叶片 ,叶氮在Rubisco的分配系数 (PR)和叶氮在生物力能学组分的分配系数 (PB)分别较对照低 8.1 %和 3.0 % ,叶氮分配到类囊体膜捕光色素蛋白组分的则略见增高 ,UV B辐射降低叶氮在光合循环组分的分配     

活性氧对外源IAA诱导的ACC合酶活性的影响

本文试图从活性氧的角度阐明外源IAA诱导ACC合酶活性的机制.绿豆(Phaseolus radiatus L.)幼苗的乙烯产生及ACC合酶活性从萌发的第5天开始上升,到第10天达到高峰,接着下降.10 μmol/L的外源IAA能明显促进绿豆幼苗乙烯的产生及ACC合酶的活性,同时也促进了超氧阴离子自由基(O(-)/(*)2)、过氧化氢(H2O2)的产生.显示外源IAA诱导的ACC合酶的活性与其诱导的活性氧的产生具有某种相关性.外源O(-)/(*)2处理能明显提高绿豆幼苗的乙烯产生速率及ACC合酶的活性,而外源H2O2无论对乙烯产生或ACC合酶的活性均没有明显的作用.外加O(-)/(*)2的清除剂SOD对绿豆幼苗乙烯的产生及ACC合酶活性的提高有一定的抑制作用,而外源过氧化氢酶却没有明显的作用.为此我们可以得出结论:外源IAA诱导的绿豆幼苗ACC合酶活性的提高可能是由于其诱导的O(-)/(*)2产生的升高引起的,这可能也是高等植物中调控乙烯生物合成的机制之一;而IAA诱导的H2O2产率的升高并不是其诱导ACC合酶活性升高的原因.     

Lys-315 at the Interfaces of Diagonal Subunits of δ-Crystallin Plays a Critical Role in the Reversibility of Folding and Subunit Assembly

δ-Crystallin is the major structural protein in avian eye lenses and is homologous to the urea cycle enzyme argininosuccinate lyase. This protein is structurally assembled as double dimers. Lys-315 is the only residue which is arranged symmetrically at the diagonal subunit interfaces to interact with each other. This study found that wild-type protein had both dimers and monomers present in 2–4 M urea whilst only monomers of the K315A mutant were observed under the same conditions, as judged by sedimentation velocity analysis. The assembly of monomeric K315A mutant was reversible in contrast to wild-type protein. Molecular dynamics simulations showed that the dissociation of primary dimers is prior to the diagonal dimers in wild-type protein. These results suggest the critical role of Lys-315 in stabilization of the diagonal dimer structure. Guanidinium hydrochloride (GdmCl) denatured wild-type or K315A mutant protein did not fold into functional protein. However, the urea dissociated monomers of K315A mutant protein in GdmCl were reversible folding through a multiple steps mechanism as measured by tryptophan and ANS fluorescence. Two partly unfolded intermediates were detected in the pathway. Refolding of the intermediates resulted in a conformation with greater amounts of hydrophobic regions exposed which was prone to the formation of protein aggregates. The formation of aggregates was not prevented by the addition of α-crystallin. These results highlight that the conformational status of the monomers is critical for determining whether reversible oligomerization or aggregate formation occurs.     

Frontal Lobe Contusion in Mice Chronically Impairs Prefrontal-Dependent Behavior

Traumatic brain injury (TBI) is a major cause of chronic disability in the world. Moderate to severe TBI often results in damage to the frontal lobe region and leads to cognitive, emotional, and social behavioral sequelae that negatively affect quality of life. More specifically, TBI patients often develop persistent deficits in social behavior, anxiety, and executive functions such as attention, mental flexibility, and task switching. These deficits are intrinsically associated with prefrontal cortex (PFC) functionality. Currently, there is a lack of analogous, behaviorally characterized TBI models for investigating frontal lobe injuries despite the prevalence of focal contusions to the frontal lobe in TBI patients. We used the controlled cortical impact (CCI) model in mice to generate a frontal lobe contusion and studied behavioral changes associated with PFC function. We found that unilateral frontal lobe contusion in mice produced long-term impairments to social recognition and reversal learning while having only a minor effect on anxiety and completely sparing rule shifting and hippocampal-dependent behavior.     

Effect of Piper betle L. and its extracts on the growth and aflatoxin production by Aspergillus parasiticus

Ground powder of the leaf and fruit of Piper betle L., a tropical spice plant grown in Southeast Asia, was prepared and extracted by chloroform, ethanol and water with one solvent only or with 3 solvents in sequence. The betel powder and various extracts were added to YES broth to determine their effects on the growth and aflatoxin production by Aspergillus parasiticus. Results showed that betel leaf powder exhibited higher antimycotic activity than fruit. One half percent of ground leaf powder completely inhibited the growth and aflatoxin production by A. parasiticus. Among the solvent extracts, chloroform and ethanol extracts of betel leaf prepared from a single solvent extraction showed more antimycotic activity. The ethanol extract of betel leaf at the level of 450 micrograms/ml would eliminate A. parasiticus growth and aflatoxin production. The antimycotic activity of this ethanol extract was most pronounced at pH 4.     

The biological functions of low-frequency vibrations (phonons) 5. A phenomenological theory

Low-frequency internal motions of a biomacromolecule are thought to possess significant biological function from the dynamic point of view. In this paper, a general phenomenological theory is established by which it is clearly verified that low-frequency resonance plays a central role in the energy transmission required during the cooperative interaction between subunits in a protein oligomer. According to the present theory, it is found that the energy transmission between a pair of diagonal subunits in a protein oligomer with a polygon arrangement is the most efficient, so as to in a sense further predict that after a ligand is bound to a subunit by random collision, its diagonal subunit in the same protein oligomer will possess the greatest probability of binding with the next ligand. Furthermore, based on the concept of the 'resonance-controlled trigger' derived from the phenomenological theory, it is feasible to estimate the lower time limit of allosteric transition from one subunit to the other. Such a time limit depends on the dominant low-frequency mode of each subunit, the ratio of the coupling force constant to the corresponding inherent force constant, as well as the geometrical arrangement of subunits in a protein oligomer. So far none of the allosteric transitions observed in proteins has exceeded the time limit as defined here, indicating a logical consistency between our theory and the experiments.     

Characterization of the Psychological,Physiological and EEG Profile of Acute Betel Quid Intoxication in Na?ve Subjects

Betel quid use and abuse is wide spread in Asia but the physiological basis of intoxication and addiction are unknown. In subjects naïve to the habit of betel quid intoxication, the psychological and physiological profile of intoxication has never been reported. We compared the effect of chewing gum or chewing betel quid, and subsequent betel quid intoxication, on psychological assessment, prospective time interval estimation, numerical and character digit span, computerized 2 choice tests and mental tasks such as reading and mathematics with concurrent monitoring of ECG, EEG and face temperature in healthy, non-sleep deprived, male subjects naïve to the habit of chewing betel quid. Betel quid intoxication, dose dependently induced tachycardia (max 30 bpm) and elevated face temperature (0.7°C) (P<0.001) above the effects observed in response to chewing gum (max 12 bpm and 0.3°C) in 12 subjects. Gross behavioral indices of working memory such as numerical or character digit span in 8 subjects, or simple visual-motor performance such as reaction speed or accuracy in a two choice scenario in 8 subjects were not affected by betel quid intoxication. Betel quid intoxication strongly influenced the psychological aspects of perception such as slowing of the prospective perception of passage of a 1 minute time interval in 8 subjects (P<0.05) and perceived increased arousal (P<0.01) and perceived decreased ability to think (P<0.05) in 31 subjects. The EEG spectral profile recorded from mental states associated with open and closed eyes, and mental tasks such as reading and eyes closed mental arithmetic were significantly modified (P<0.05) relative to chewing gum by betel quid intoxication in 10 subjects. The prevalence of betel quid consumption across a range of social and work settings warrants greater investigation of this widespread but largely under researched drug.