Identification and Characterisation of a New PTS1 Motif in Plants

Peroxisomes, as one of the last major cellular organelle to be discovered, play important role in photosynthesis and lipid mobilisation. Proteins are targeted to peroxisome mainly by a conserved peroxisome targeting signal namely type 1 (PTS1) or type 2 (PTS2). Traditionally, PTS1 type proteins are believed to be recognised by their last 3 amino acids motif and a few adjacent amino acids. 

In this study, we aim to identify and characterize a C-terminal motif of Serine-Asparagine-Leucine (SNL) in Arabidopsis, and to investigate the possible mechanisms about how the sequence affects peroxisome targeting. The last 30 amino acids of all the 13 genes with a C-terminal of SNL were cloned and transiently expressed in A. thaliana suspension cell. We found that 9 out of the 13 candidate genes showed peroxisome targeting and these proteins could no longer be targeted to peroxisome after the last 3 amino acids form the C terminal were deleted, indicating the SNL is likely a newly discovered peroxisome targeting signal. In addition, we also investigated the effect of adjacent positions on peroxisome targeting, via cloning different length of deleted sequences and site-directed mutant sequences. The results suggest that the adjacent sequences may have further impact on peroxisome targeting.