[Primary structure of bovine erythrocyte carbonic carbonic anhydrase CI. II. Complete sequence]

Cleavage of bovine carbonic anhydrase CI by cyanogen bromide at the 3 methionine residues yields 4 fragments which were isolated by insolubilisation (IICNBr) and gel filtration on Sephadex G-50 in alkaline medium (ICNBr, IIICNBr, IVCNBr). Sequence studies performed on these fragments allowed the alignment of the 64 first residues (tryptic units T1 to T7) and the 89 last residues (tryptic units T19 to T26) of the polypeptide chain. From a tryptic hydrolysate of the maleylated protein arginylpeptides M1 to M10 have been isolated by gel filtration on Sephadex G-50 followed by purification of heterogeneous fractions. Investigations on M4 and M6 achieved the determination of the primary structure of the bovine carbonic anhydrase CI. Its comparison with the sequence of human B and C and ovine C erythrocyte carbonic anhydrases was discussed in connection with the actual data concerning the three-dimensional structure and the catalytic mechanism of the carbonic anhydrase isozymes.