Synaptic localization of kainic acid binding sites

The heterocyclic compound kainic acid (KA) is a potent excitant when applied to mammalian neurones. Lesions caused by injections of KA into the rat striatum and hippocampus cause similar patterns of damage to those seen in Huntington's chorea and status epilepticus, respectively. Although it was originally thought to be a glutamate agonist, it is now clear that KA does not act on the majority of the receptors for glutamate, and in fact seems to act on a class of receptors which are distinct from those which mediate responses to other excitatory amino acids. The potent and selective neurotoxic effects of this compound may be mediated by these same receptors. At present, the relative distribution of junctional and extrajunctional (non-synaptic) receptors is unknown and resolution of this issue would provide important insights into the action of KA on the central nervous system (CNS). We show here that KA binding sites are greatly enriched in isolated synaptic junctions from rat brain and, using an in vitro autoradiographic technique, we have found that these binding sites are concentrated specifically in terminal fields where KA acts as a potent neurotoxin.     

Molecular structure of F-actin and location of surface binding sites

Comparisons of three-dimensional maps of vertebrate muscle thin filaments obtained by cryo-electron microscopy and image analysis, reveal the molecular structure of F-actin, the location of the C terminus of the monomer and the positions of the binding sites of tropomyosin, the myosin head and the N-terminal portion of the myosin A1 light chain on the filament. These data provide strong constraints for evaluating models built from the atomic structure of the monomer and the subsequent identification of molecular contacts.     

配体叠合的蛋白质结合部位结构多样性的分析

蛋白质结构与功能间关系的一个重要方面是蛋白质与配体的识别和结合能力问题.本文通过探寻与同一个配体（HEM）相作用的74个非同源蛋白质上活性位点的潜在规律来分析蛋白质的结构,综合应用编程、数据处理及图像分析等手段对蛋白质及配体的叠合进行研究,为用3D-QSAR方法研究蛋白质的结构提供了可能.     

Spatial relationship of the Fis binding sites for Hin recombinational enhancer activity

Site-specific recombination reactions involve the joining or rearrangement of discrete DNA segments in a highly precise manner. A site-specific DNA inversion regulates the expression of flagellin genes in Salmonella by switching the orientation of a promoter. Analysis of the reaction has shown that, in addition to DNA sequences at the two boundaries of the 1-kilobase invertible segment where strand exchange occurs, another cis acting sequence is required for efficient inversion. This 60-base-pair enhancer-like sequence can function at many different locations and in either orientation in a plasmid substrate. It includes two binding sites for a host protein called Factor II or Fis (refs 4 and 5). Here we have investigated the importance of the spatial relationship between the two Fis binding sites for enhancer activity and have found that the correct helical positioning of the binding sites on the DNA is critical. However, this result could not be accounted for by effects on Fis binding. We propose a model for enhancer function in which the enhancer region acts to align the recombination sites into a specific conformation required for productive synapsis.