Amino-terminal sequence of spinach chloroplast fructose-1,6-bisphosphatase

The sequence of the NH2-terminal 25-amino acid residues of purified spinach chloroplast fructose-1,6-bisphosphatase was determined by automated Edman degradation. The amino acid sequence is as follows: Ala-Ala-Val-Gly-Glu-Ala-Ala-Thr-Gln-Thr-Lys-Ala- Arg-Thr-Arg-Ser-Lys-Tyr-Glu-Ile-Glu-Thr-Leu-Thr-Gly. A comparison of this sequence with the corresponding region of pig kidney and yeast (Saccharomyces cerevisiae) fructose-1,6-bisphosphatases shows that the sequence of residues 1-19 of the chloroplast enzyme has no homology with the other fructose-1,6-bisphosphatases, but homology is evident after residue 20. The dissimilar sequence contains a region (residues (8-17) rich in basic and hydroxylated amino acids, a structure which is typical of presequences of mitochondrial and chloroplast proteins. Since chloroplast fructose-1,6-bisphosphatase is nuclear in origin, these results suggest that the chloroplast targeting region may have been retained within the amino acid sequence of the mature protein.