Abstract. In neuronal axons, various kinds of membranous components are transported along microtubules bidirectionally. However, only two kinds of mechanochemical motor proteins, kinesin and brain dynein, had been identified as transporters of membranous organelles in mammalian neurons. Recently, a series of genes that encode proteins closely related to kinesin heavy chain were identified in several organisms including Schizosaccharomyces pombe, Aspergillus niddulans, Saccharomyces cerevisiae, Caenorhabditus elegans, and Drosophila. Most of these members of the kinesin family ale implicated in mechanisms of mitosis or meiosis. To address the mechanism of intracellular organelle transport at a molecular level, we have cloned and characterized five different members , that encode the microtubule-associated motor domain homologous to kinesin heavy chain, in murine brain tissue. Homology analysis of amino acid sequence indicated that KIF1 and KIF5 are mufine counterparts of uric/04 and kinesin heavy chain, respectively, while KIF2, KIF3, and KIF4 are as yet unidentified new species. Complete amino acid sequence of KIF3 revealed that KIF3 consists of NH2-terminal motor domain, central a-helical rod domain, and COOH-terminal globular domain. Complete amino acid sequence of KIF2 revealed that KIF2 consists of NH~-terminal globular domain, central motor domain, and COOH-terminal or-helical rod domain. This is the first identification of the kinesin-related protein which has its motor domain at the central part in its primary structure. Northern blot analysis revealed that KIFI, KIF3, and KIF5 are expressed almost exclusively in murine brain, whereas KIF2 and KIF4 are expressed in brain as well as in other tissues. All these members of the kinesin family are expressed in the same type of neurons, and thus each one of them may transport its specific organelle in the murine central nervous system.

Two monoclonal antibodies (SPM-1 and SPM-2) immunoprecipitate brain N-type calcium channels. On immunoaffinity chromatography of digitonin extracts of bovine brain membranes on SPM-l-and SPM-2Sepharose, proteins of 36 (syntaxins A and B), 28 and 19 kDa are specifically retained by both columns. Here we show that the 19 and 28 kDa bands contain VAMPIsynaptobrevin-2, and rab3A/smg25A and SNAP-25, respectively. Since SPM-1 and SPM-2 recognize only syntaxins and the 28 kDa band (rab3AIsmg25A and SNAP-25), respectively, the results indicate that all these proteins form a complex. Our results suggest tight linkage between the components involved in neurotransmitter release.Rab3A/smg25A; Syntaxin; VAMP/synaptobrevin-2; SNAP-25; Neurotransmitter release

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We have previously identified two membrane proteins (36 kDa and 28 kDa) associated with co-conotoxin GVIA-sensitive (N-type) calcium channels in the brain. Partial amino acid sequences and immunoblot analysis after sodium dodecyl sulfate-electrophoresis in urea indicated the presence of several isoforms (synaptocanalins) of the 36 kDa protein in the brain. The amino acid sequence of one form of the 36 kDa protein (named synaptocanalin

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