Spinach carbonic anhydrase primary structure deduced from the sequence of a cDNA clone.

A cDNA clone 1,156 base pairs in length was selected by screening a lambda gt11 library with antibodies directed against spinach chloroplast carbonic anhydrase (carbonate dehydratase, EC 4.2.1.1). Sequence analysis revealed an open reading frame of 957 base pairs encoding a polypeptide containing 319 amino acids with a molecular weight of 34,569. This polypeptide is of sufficient size to represent the precursor of spinach chloroplast carbonic anhydrase. The polypeptide contains a sequence of 19 amino acids identical to the sequence of a cyanogen bromide fragment from spinach carbonic anhydrase. In addition, Escherichia coli was transformed with a plasmid that expresses spinach carbonic anhydrase. Lysates prepared from transformed E. coli contain acetazolamide-inhibitable carbonic anhydrase activity. The amino acid sequence of spinach carbonic anhydrase is distinct from those reported for the mammalian isozymes.