Abstract
In the filamentous fungus Neurospora crassa the biosynthesis of carotenoids is regulated by blue light. Here we report the characterization of the albino-3 (al-3) gene of N. crassa, which encodes the carotenoid biosynthetic enzyme geranylgeranyl-pyrophosphate synthetase. This is the first geranylgeranyl-pyrophosphate synthetase gene isolated. Nucleotide sequence comparison of al-3 genomic and cDNA clones revealed that the al-3 gene is not interrupted by introns. Transcription of the al-3 gene has been examined in dark-grown and light-induced mycelia. The analysis revealed that the al-3 gene is not expressed in the dark and that its transcription is induced by blue light (Nelson, M. A., Morelli, G., Carattoli, A., Romano, N., and Macino, G. (1989) Mol. Cell. Biol. 9, 1271-1276). The al-3 gene encodes a polypeptide of 428 amino acids. Comparison of the deduced amino acid sequence of al-3 with the sequences of prenyltransferases of other species, from bacteria to humans, showed three highly conserved homologous regions. These homologous regions may be involved in the formation of the catalytic site of the prenyltransferases.
Highlights
Inthe filamentous fungus Neurosporacrassa the Albino 3 mutants are defective in GGPP’ synthetase biosynthesis of carotenoids is regulated by blue light. [5], while albino 2 and albino 1 mutantsare defective in
In previous work we isolated the gene encoding biosynthetic enzyme geranylgeranyl-pyrophosphate GGPP synthetase from N . crmsa by complementation of the synthetase. This is the first geranylgeranyl-pyrophos- al-3 mutant;expression studies showed that thetranscription phate synthetase gene isolated
Nucleotide sequence of the al-3gene is controlled by light regulation [1]
Summary
For abscissic acid biosynthesis in plants. In Neurospora crassa the biosynthesis of carotenoids is regulated byblue light in the mycelium but is constitutive inthe asexual spores [3,4,5]. Brems et al [32] identified this region by a site-directed photoaffinity label on the Domeln II purified enzyme and proposed thatthe arginine residue (whose position is indicated in Fig. 5 with an asterisk), conserved in human and rat FPP synthetase (not shown) andsubstituted by lysine in all the other known prenyl transferases, could be responsible for the binding of the pyrophosphate group. These authors showedevidenceof the involvement of 2 arginine residues in the function of al-3 u#I [ F O I ~ NL crtE prenyltransferases. -LGE F Q l ODDVL C and a stronger homology with the third domain, in which all mod
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
