26] Evolutionary conservation and structural similarities of carotenoid biosynthesis gene products from photosynthetic and nonphotosynthetic organisms

Abstract

Publisher Summary Carotenoids have attracted considerable interest as a major class of natural pigments with important roles in photosynthesis, nutrition, and photooxidative protection. Recent developments in the molecular description of carotenoid biosynthesis genes from photosynthetic bacteria, non-photosynthetic bacteria, and fungi offer powerful indirect approaches for predicting the structural properties of the gene products. This chapter describes methods useful for the comparison and analysis of the deduced amino acid sequences of carotenoid biosynthesis enzymes from these organisms. It also discusses the significance of sequence similarities between these proteins and other gene products from computer databases in terms of the biosynthetic reactions catalyzed and cofactor requirements. The specific biosynthetic pathways operating in Rhodobacter capsulatus , in Escherichia coli expressing cloned Erwinia crt genes, and in Neurospora crassa are summarized in the chapter. Three genetic loci necessary for the synthesis of phytoene from geranylgeranyl pyrophosphate via prephytoene pyrophosphate and phytoene and dehydrogenation have been identified in R. capsulatus . Cognate genes have been identified in Erwinia by comparisons of deduced sequence similarities between the R. capsulatus and Erwinia gene products and by mutational analyses.