| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1992: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1991: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
65-kilodalton protein has been characterized as an interleukin 2-stimulated phosphoprotein in human T cells. We determined the complete primary structure of p65 based on the cDNA isolated from a human T lymphocyte (KUT-2) cDNA library. Analysis of p65 sequence indicated that p65 is multidomain molecule involving at least three intriguing domains; two putative calcium-binding sited along the N- terminal 80 amino acid residues; a putative calmodulin-binding site following the calcium binding region; and two tandem repeats of putative actin-binding domains in its middle and C-terminal parts, each containing approximately 240 residues. This domain structure closely resembles a chicken intestinal microvilli protein, fimbrin, that bundles actin filaments. It was observed that unphosphorylated L-plastin isolated from human T cells bundles F-actin just as fimbrin does. L-plastin acted on T cell beta-actin, but hardly acted on muscle alpha-actin or chicken gizzard gamma-actin, whereas fimbrin bundles alpha-actin. Unlike fimbrin, L-plastin's actin-bundliung action was strictly calcium-dependent: the bundles were formed at pCa 7, but not at pCa 6. Under suitable conditions, approximately one molecule of L-plastin bound to 8 molecules of actin monomer in the actin filament.
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