由氨基酸序列预测蛋白质二级结构的进一步研究

本文在工作[1][2]的基础上进一步研究了蛋白质二级结构的经验预测,着重讨论了如何制定预测规则的问题,并将预测工作计算机化.在蛋白质资料库中随机选取了21个蛋白质(3296残基)进行预测,正确率对α螺旋和β折迭分别为84.4%和81.9%.     

S-Nitrosylation of proteins

The transfer of a nitric oxide group to cysteine sulfhydryls on proteins, known as S-nitrosylation, is increasingly becoming recognized as a ubiquitous regulatory reaction comparable to phosphorylation. It represents a form of redox modulation in diverse tissues, including the brain. An increasing number of proteins have been found to undergo S-nitrosylation in vivo. These proteins are called S-nitrosothiols, and may play an important role in many processes ranging from signal transduction, DNA repair, host defense, and blood pressure control to ion channel regulation and neurotransmission. This review focuses on the importance of the S-nitrosylation reaction and describes some recently identified S-nitrosothiols in various fields of research.     

Molecular pathogenesis of apolipoprotein E-mediated amyloidosis in late-onset Alzheimer’s disease

Apolipoprotein E (apoE) ɛ4 allele is a genetic risk factor for late-onset familial and sporadic Alzheimer’s disease (AD). In the central nervous system, apoE is secreted mainly by astrocytes as a constituent of high-density lipoproteins. A recent study using apoE knockout mice provided strong evidence that apoE promotes cerebral deposition of amyloid β protein (Aβ). However, no clear explanation of the pathogenesis of apoE-induced AD has been provided. Here we discuss two possible mechanisms by which apoE might enhance Aβ deposition. One is the intracellular pathway in which apoE is internalized by neurons and induces lysosomal accumulation of Aβ and amyloidogenic APP (amyloid precursor protein) fragments, leading to neuronal death. The other is the extracellular pathway in which apoE-containing lipoproteins are trapped by Aβ1–42 deposits mobilizing soluble Aβ peptides and consequently enlarge amyloid plaques. These two mechanisms may operate at different stages of AD pathogenesis and suggest a chaperone-like function for the apoE molecule. Received 4 February 1999; received after revision 9 April 1999; accepted 23 April 1999     

MAP kinases in plant signal transduction

Mitogen-activated protein kinase (MAPK) pathways are modules involved in the transduction of extracellular signals to intracellular targets in all eukaryotes. Distinct MAPK pathways are regulated by different extracellular stimuli and are implicated in a wide variety of biological processes. In plants there is evidence for MAPKs playing a role in the signaling of abiotic stresses, pathogens and plant hormones. The large number and divergence of plant MAPKs indicates that this ancient mechanism of bioinformatics is extensively used in plants and may provide a new molecular handle on old questions.     

Myosins from plants

Molecular cloning and sequence analysis of myosin genes from Arabidopsis thaliana and electron microscopic observation of a myosin from characean alga have revealed that overall structure of plant unconventional myosins is similar to that of the class V myosins. These plant unconventional myosins have two heads, a coiled-coil tail of varied length and a globular tail piece at the end. The tail piece is probably a site for membrane interaction. Characean myosin is of special interest because it can translocate actin filaments at a velocity several times faster than muscle myosin, which must have evolved to support the quick movement of animals in the struggle for their lives.     

盐法分离低核酸酵母蛋白的机理研究

本文用荧光光谱法研究了不同盐对酵母蛋白质构象的影响,结果表明,盐是降低酵母蛋白分离物的核酸含量的原因之一。通过对盐除核酸过程进行热力学分折,对比离子对水结构和核蛋白稳定性的影响,否定了Damodaran提出的疏水作用机理,证明在维持核蛋白稳定的次级键中,氢键的作用是最主要的;核蛋白的解离并非盐通过改变溶剂的结构而间接作用于核蛋白所致,而应归因于盐与核蛋白的直接作用,特别是盐与核蛋白分子主链的作用。     

金属膜对L-缬氨酸发酵液过滤的研究

研究了金属膜过滤的各种操作参数对L-缬氨酸过滤效果的影响，综合各方面的因素确定了最适工艺条件：进出膜压力分别为4．0MPa和3．0MPa，过滤温度为25℃，过滤液pH为3．0。在此操作条件下，蛋白质去除率达到87．36％以上，色素去除率达48．61％，L-缬氨酸收率达90．2％。     

The effect of cycloheximide on nuclear uH2A content

Summary The effect of intraperitonal cycloheximide administration on acid-soluble rat liver chromatin proteins has been investigated by electrophoresis in acetic acid-urea polyacrylamide gels. A nonhistone protein, which migrates between oxidized histone H3 and histone H1 has been found tobe increased in amount following cycloheximide treatment. This protein seems to be identical with semihistone protein H24 (uH2A). A possible relationship of uH2A to the inhibition of rRNA synthesis is discussed.This work was supported by the Turkish Scientific and Technical Research Council (TUBITAK) Project No. TAG 339     

High molecular transport proteins for JH-III in insect hemolymph

Summary Using two independent techniques, ultracentrifugation in a KBr-gradient, and native pore polyacrylamide gel electrophoresis in combination with [³H]-epoxyfarnesyldiazoacetate photoaffinity labeling, we showed that in the hemolymph ofPeriplaneta americana, and probably also inLeptinotarsa decemlineata JH-III binds to the lipophorin, whereas inLocusta migratoria JH-III binds to a different protein.