| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2004: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2003: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Research Abstract |
Calcium signaling mechanisms are widely employed by all eukaryotic organisms to regulate gene expression and a variety of cellular processes. In plants, many extracellular signals, such as light, drought, cold, salinity, stress factors, elicit changes in cellular calcium concentration. The calcium sensor protein often changes its conformation in a calcium-dependent manner and interacts with other signaling proteins to relay the signal. Several families of calcium sensor proteins have been identified in higher plants. Recently, novel calcium sensor proteins with EF-hand motifs from Arabidopsis thaliana have been identified, referred to as AtCBL(Arabidopsis thaliana calcineurin B-like protein). A family of SNF1 has been identified as targets for CBL proteins(7-9).These are serine-threonine protein kinases, referred to as AtCIPK(Arabidopsis thaliana CBL-interacting protein kinase), that form a novel family of proteins found so far only in plants.
The crystal structure of AtCBL2 has been determined at 2.1A resolution. The protein forms a compact a-helical structure with two pairs of EF-hand motifs. The structure is similar in overall folding topology to the structures of calcineurin B and neuronal calcium sensor 1 , but differs significantly in local conformation. The two calcium ions are coordinated in the first and fourth EF-hand motifs, while the second and third EF-hand motifs are maintained in the open form by internal hydrogen bonding without coordination of calcium ions. Both a possible site and a possible mechanism for the target binding to AtCBL2 are discussed based on the three-dimensional structure.
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