Expression of Genes for Plant-Type Rubisco in Chromatium and Escherichia Coli

Abstract

Molecular mechanisms governing the biosynthesis of two constituent subunits (A and B) of RuBisCO and their functional roles in the enzyme reaction have received a great deal of attention from many investigators (1). RuBisCO is well known as one of light- inducible enzymes in higher plants (2). Detailed regulatory mechanisms of expression of RuBisCO genes have not been clarified, although upstream DNA sequences of the genes have been reported to be responsible for light induction (3). Since genes for the subunits are encoded by chloroplast and nuclear genomes in higher plants (2), it is frequently argued whether or not a synchronous mechanism operates in the biosynthesis of two subunits to make up the enzymi-cally active holoenzyme in chloroplasts. In order to solve these problems, Chromatium uinosum, a photosynthetic purple sulfur bacterium, is thought to be a feasible material from the following reasons. (i) Chromatium is one of the most primitive organisms, yet containing a plant-type RuBisCO molecule (AgBg) (1,4). (ii) Inducible formation of RuBisCO molecules occurs under autotrophic growing condition after the initial heterotrophic culture.