Isolation of an Arabidopsis cDNA sequence encoding a 22 kDa calcium-binding protein (CaBP-22) related to calmodulin.
Complementary DNA sequences were isolated from a library of cloned Arabidopsis leaf mRNA sequences in lambda gt10 that encoded a 21.7 kDa polypeptide (CaBP-22), which shared 66% amino acid sequence identity with Arabidopsis calmodulin. The putative Ca(2+)-binding domains of CaBP-22 and calmodulin, however, were more conserved and shared 79% sequence identity. Ca2+ binding by CaBP-22, which was inferred from its amino acid sequence similarity with calmodulin, was demonstrated indirectly by Ca(2+)-induced mobility shifting of in vitro translated CaBP-22 during SDS-polyacrylamide gel electrophoresis. CaBP-22 is encoded by a ca. 0.9 kb mRNA that was detected by northern blotting of leaf poly(A)+ RNA; this mRNA was slightly larger than the 809 bp CaBP-22 cDNA insert, indicating that the deduced amino acid sequence of CaBP-22 is near full-length. CaBP-22 mRNA was detected in RNA fractions isolated from leaves of both soil-grown and hydroponically grown Arabidopsis, but below the limits of detection in RNA isolated from roots, and developing siliques. Thus, CaBP-22 represents a new member of the EF-hand family of Ca(2+)-binding proteins with no known animal homologue and may participate in transducing Ca2+ signals to a specific subset of response elements.
Ling
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Department of Plant Biology, University of Illinois, Urbana 61801.
Zielinski
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D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D001483:Base Sequence; D002135:Calcium-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D002147:Calmodulin / Q000235:genetics; D003001:Cloning, Molecular; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014158:Transcription, Genetic
D002135:Calcium-Binding Proteins; D002147:Calmodulin; D012333:RNA, Messenger; C081673:calcium-binding protein, Arabidopsis