Bacteria sorting pathways

The individual steps in the elongation of the fatty acid chain are quite similar in bacteria, fungi, plants, and animals. The ease of purification of the separate enzymes from bacteria and plants made it possible in the beginning to sort out each step in the pathway, and then by extension to see the pattern of biosynthesis in animals. The reactions are summarized in Figure 25.7. The elongation reactions begin with the formation of acetyl-ACP and malonyl-ACP, which... 

As described in Section II,A, gram-positive bacteria have only one membrane (the cytoplasmic membrane). Therefore, the translocation through the Sec pathway directly leads proteins to be secreted (Simonen and Palva, 1993 Nagarajan, 1993). The issue of protein sorting into the cell wall is described in a separate section. 

In the first part of the chapter, we cover targeting of proteins to the ER, Including the post-translatlonal modifications that occur to proteins as they enter the secretory pathway. We then look at several mechanisms for exporting proteins from bacteria, some of which are similar to protein sorting In eukaryotic cells. The last two sections describe targeting of proteins to mitochondria, chloroplasts, and peroxisomes. We cover the transport of proteins In and out of the nucleus through nuclear pores In Chapter 12 because nuclear transport Is Intimately related to post-transcriptlonal events and Involves several nucleus-specific variations on the mechanisms discussed In this chapter. 

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