Bartley G E, Scolnik P A
Du Pont Plant Science Group, Central Research and Development Department, Wilmington, Delaware 19880-0402.
J Biol Chem. 1989 Aug 5;264(22):13109-13.
Carotenoids are photoprotective pigments present in many photosynthetic and nonphotosynthetic organisms. The desaturation of phytoene into phytofluene is an early step in the biosynthetic pathway that in the photosynthetic bacterium Rhodobacter capsulatus is mediated by the product of the crtI gene. Here we report the sequence of this gene and the identification of CrtI as a membrane protein of approximate Mr 60,000. Mutant strains with 5-fold lower or 10-fold higher levels of CrtI with respect to wild type have only small differences in their carotenoid content, indicating that the cellular concentration of CrtI is not a limiting factor in carotenoid biosynthesis. However, a correlation was found between the levels of CrtI and the formation of a photosynthetic antenna system.
类胡萝卜素是存在于许多光合和非光合生物中的光保护色素。八氢番茄红素去饱和生成六氢番茄红素是生物合成途径中的早期步骤，在光合细菌荚膜红细菌中，该步骤由crtI基因的产物介导。在此，我们报道了该基因的序列，并鉴定出CrtI是一种分子量约为60,000的膜蛋白。与野生型相比，CrtI水平降低5倍或升高10倍的突变菌株，其类胡萝卜素含量仅有微小差异，这表明CrtI的细胞浓度不是类胡萝卜素生物合成的限制因素。然而，发现CrtI水平与光合天线系统的形成之间存在相关性。
