CLONING AND SEQUENCING OF THE GENE ENCODING SPINACH FERREDOXIN-DEPENDENT GLUTAMATE SYNTHASE

The nucleotide sequences of two cDNA clones, totalling 4948 bp in length, encoding 98% of the 1483 amino acids of the mature form of the ferredoxin-dependent glutamate synthase of spinach chloroplasts have been determined. The amino-terminal sequence of the enzyme has been determined by direct sequencing of the protein. The deduced amino-acid sequence of the spinach enzyme is 83% identical to that of the ferredoxin-dependent maize enzyme and shows significant sequence homology to two prokaryotic NAD(P)H-dependent glutamate synthases. Analysis of spinach genomic DNA indicates the presence of a single-copy gene for the spinach enzyme. Northern analysis reveals the presence of a single 5.5 kb transcript, which is present in higher levels in young spinach leaves than in older leaves.