Peptides, chloroplast transit

As described earlier, translation of the EPSPS mRNA of plants results in the formation of a protein which has an AJ-terminal extension. The AJ-terminal extension, referred to as the chloroplast transit peptide, is necessary and sufficient for the import of the preprotein by the chloroplast. Once imported by the chloroplast, the transit peptide is cleaved releasing the mature enzyme. As expected, introduction of the EPSPS transit peptide to other protein sequences results in the importation of the fusion protein by the chloroplast. 

Chloro pink, 9 310-311 Chloroplast transit peptide, 72 489 TV-Chloropolyacrylamides, 7 316 Chloroprene, 6 242, 246. See also 2-Chloro-1,3- butadiene from butadiene, 4 369 chlorocarbon/chlorohydrocarbon of industrial importance, 6 227t copolymerization of, 79 829-830 end use of chlorine, 6 134t removal in vinyl chloride manufacture, 25 642... 

Although the chloroplast transit peptide has been studied relatively thoroughly, further intrachloroplastic sorting signals have not been well understood. Some of them are introduced below in the context of describing the known sorting pathways (Keegstra and Cline, 1999 Chen and Schnell, 1999 Cline and Henry, 1996 Kouranov and Schnell, 1996). 

Emanuelsson, O., Nielsen, H., and von Heijne, G. (1999). ChloroP, a neural network-based method for predicting chloroplast transit peptides and their cleavage sites. Protein Sd. 8, 978—984. 

The coding sequences of a- and P-globins of human hemoglobin have been fused to the sequence of the chloroplastic transit peptide of the small subunit of Rubisco. These proteins were then coexpressed in transgenic tobacco plants, resulting in the production of a functional form of tetra-meric hemoglobin. The results demonstrate that a complex multimeric protein such as recombinant human hemoglobin can be obtained from tobacco in a functional form. 

Y Gavel, GA von Hejne. A conserved cleavage-site motif in chloroplast transit peptides. FEBS Lett 261 455-458, 1990. 

Bruce, B. D. 2000. Chloroplast transit peptides Structure, function and evolution. Trends Cell Biol 10 440-7. 

Target (htq) //www.cbs.dtu.dk/servicesA argetP/) assigns the subcellular location of proteins based on the predictions of the N-terminal chloroplast transit peptide, mitochondrial targeting peptide or secretory signal peptide. 

AMPHIPATHIC )5-SHEET DOMAINS IN CHLOROPLAST TRANSIT PEPTIDES... 

Acknowledgment, This research was supported by NIH grant GM-38323 (WAC) and DOE grant 86ER13526 (KK). The authors thank G. von Heijne for a preprint of ref. 5 that is the first published report of prominent -structure in chloroplast transit peptides. 

Amphipathic p-Sheet Domains in Chloroplast Transit Peptides 799... 

Fifteen clones from the developing embryo cDNA library were isolated and partially sequenced. The longest cDNA insert contained 1667 bp excluding the poly(A) tail, with 67 bp of 5 untranslated leader sequence. The deduced amino acid sequence encoded by the open reading frame consists of 533 amino acids. It has 82% and 52% identity with the N.tabacum and E.coli biotin carboxylases respectively. Tht B.napus biotin carboxylase contains an extra 70 aa N-terminal fragment compared to the prokaryotic forms. This fragment is presumed to be the chloroplast transit peptide. 

Out of the 760 aa of the deduced amino acid sequence 308 residues (92-400) align with the prokaryotic CTas. An extra T, S, R rich 91 aa polypeptide (probably the chloroplast transit peptide) is present at the N-terminus part of the protein (1-91). The C-terminal aa sequence (360-7 ) shows homology only with the pea IEP96 and the Glycine max CTa . 

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