Research On The Nuclear Localization Signals Of CBP60g From Arabidopsis Thaliana

The nuclear pore complex (NPC) of eukaryotic cells is important for charging of macromolecules between the cytoplasm and the nuclei separated by nuclear membranes. The mode of passing through NPC is decided by the proteins’molecular weights, it must only pass through NPC by active transport if that its molecular weights is larger than 50kD. There must be one or more special signals which called nuclear localization signal (NLS) in its amino acid sequences.CBP60 proteins (CBP60s) belong to the calmodulin-binding protein family which is only present in plant. CBP60s have eight members in Arabidopsis, CBP60a-g and SARD1. Previous study revealed that CBP60g was a DNA-binding protein, altered the expression of ICSI that was induced by pathogen, and activated SA accumulation. CBP60g was located at the nuclei, but there is no classical NLS (cNLS) in the amino acid sequence of CBP60g had been predicted.To explore the NLS in the amino acid sequence of CBP60g,.the truncated cDNA sequence of CBP60g was amplified by RT-PCR method, and fused with GFP reporter gene using In-Fusion technology in this study. Using the transient expression system of Arabidopsis mesophyll protoplasts, our result suggested that the amino acid sequence of CBP60g-2-1 (position 1-84 amino acid of CBP60g), CBP60g-2-3(position 130-163 amino acid of CBP60g) and CBP60g-2-4 (number 163-306 amino acid of CBP60g) had the NLS. indicating that CBP60gmight have not only one NLS. Further study revealed that the arginines at the position 134.156 and 162 of CBP60g was important to the NLS.