Biochemical Connections Chloroplast Genes

The nuclear gene is translated in the cytoplasm, and the protein is then transported to the chloroplast, protected by a chaperonin, via targeting mechanisms (see Section 12.6 and the Biochemical Connections box on page xxx). Special targeting sequences are used to direct various nuclear products to the appropriate chloroplast location, using reactions that require ATP hydrolysis. The chaperonin aids in formation of the final, active complex. 

The chloroplast encodes its own RNA polymerase, ribo-somal and transfer RNAs, and about one-third of the ribosomal proteins. 

The DNA polymerase, aminoacyl synthetases, and the rest of the ribosomal proteins come from the nuclear genes. Different nuclear genes may be used for chloroplasts in different, specialized tissues of the plant In different classes of plants, differ- 

The most-studied is signaling by Mg-protoporphyrin IX, a tetrapyrrole generated during chlorophyll biosynthesis. Also 

What is different about CO2 fixation in tropical plants  

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