Primary structure of maize pyruvate, orthophosphate dikinase as deduced from cDNA sequence.

We have isolated two overlapping cDNA clones that encompass the entire structural gene for pyruvate, orthophosphate dikinase from maize. The analysis of the nucleotide sequence has revealed that the cDNA clones include an insert of a total of 3,171 nucleotides without a poly(A) tail and encode a polypeptide that contains 947 amino acid residues and has a molecular weight of 102,673. Comparison of the N-terminal amino acid sequence of purified pyruvate, orthophosphate dikinase protein with that deduced from the nucleotide sequence shows that the mature form of pyruvate, orthophosphate dikinase in the maize chloroplast consists of 876 amino acid residues and has a molecular weight of 95,353. The amino acid composition of the deduced sequence of pyruvate, orthophosphate dikinase is in good agreement with that of the purified enzyme. The region that contains the active and regulatory sites of pyruvate, orthophosphate dikinase can be found in the deduced sequence of amino acids. We have predicted the secondary structure and calculated the hydropathy pattern of this region. The extra 71 residues at the N terminus of the deduced sequence of amino acid residues corresponds to the transit peptide which is indispensable for the transport of the precursor protein into chloroplasts. We have compared the primary structure of the pyruvate, orthophosphate dikinase transit peptide to those of other proteins and found sequences similar to the consensus sequences found in other transit peptides.