Effects of Different Alternative Splicing of Arabidopsis CaM5 on Its Protein-binding Activity

Abstract:

Calcium (Ca²⁺)/calmodulin (Cam) signals are involved in the regulation of plant growth and development and response to external stimuli. The Arabidopsis thaliana contains seven genes in CaM family, which encoding proteins with highly conserved amino acid sequence. The protein binding activities of CaM5 splicosomes CaM5.1 and CaM 5.3 were analyzed by yeast two-hybrid and bioinformatics analysis. The results showed that the Arabidopsis calmodulin-binding protein (CaMBP) IQM3 (IQ motif-containing protein 3) could bind to members of CaM family except CaM5.3 in yeast. The bioinformatic analysis revealed that CaM5.3 had one more C-terminal domain (CTD) consisting of 35 amino acid residues than CaM5.1 and other CaM subtypes, which might affect the binding of CaM5.3 to IQM3. CTD of CML10 was added to the C-terminal of CaM5.1, the recombinant protein was binded to IQM3, confirming that CTD of CaM5.3 was the key sequence affecting its binding to IQM3. Therefore, different splicing modes of CaM5 in A. thaliana affect its protein-binding activity, which providing reference for studying the binding activities of calmodulin and calmodulin-binding proteins.

Key words:CaM;Alternative splicing;IQM3;Protein-binding activity