| Chloroplasts are semiautonomous cell organelles that containonly a limited coding information for their constituents. Most proteins present in chloroplasts are synthesized in the cytosol and are post translationally translocated into the organelle. The protein transport proceed depends on the chloroplast protein import machinery in the envelope,Toc33 is one of the components of the chloroplast protein import machinery that mediates the initial stage of protein import into chloroplastBy using PCR with primers designed according to conserve regions of the Toc33 sequence of Arabidopsis thaliana, four homologous DNA sequences were directly amplified from the genomic DNA of Orychophragmus violaceus and Brassica napus. The PCR fragments were cloned and confirmed by PCR and restriction enzyme digestion. Sequence analysis showed that the sequences from Orychophragmus violaceus were 1475bp and 1573bp, named OvToc33-land OvToc33-2. The other two sequences from Brassica napus were 1370bp and 1490bp, named BnToc33-land BnToc33-2. Their complete coding region were defined according to the Arabidopsis thaliana Toc33 mRNA, the open reading frames were 894bp long and their deduced amino acid sequences showed more than 90%identity with each other and with Arabidopsis thaliana Toc33 amino acid sequence.By using RT-PCR technique, a Toc33 cDNA was amplified from the Rape seedling RNA, the cDNA was 894bp long, named BnToc33-c, coding an 297 AA, 33KD protein. The GTP-binding motif and the presumed carboxyl terminal membrane anchor are also conserved in this Toc33 protein, BnToc33-c also shows very high identity with the deduced AA sequences of OvToc33 and BnToc33, but it is still distinguish with the cDNA deduced from the BnToc33-l and BnToc33-2.The homologous comparison of the BnToc33-c amino acid sequence also shows identity to some other GTP-binding proteins, such as AtToc33, AtToc34, PsToc34 and ZmToc34, the result showed that the sequences are highly conserved.
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