Further characterization of Nostoc verrucosum ferredoxins

Nostoc verrucosum ferredoxins Fd I and Fd II were found to have different amino acid compositions. Fd I had 98 amino acid residues of Trpo, Lys4, His1, Arg1, Asp14, Thr8, Ser6, Glu14, Pro4, Gly7, Ala10, Cys4, Val5, Met0, Ile6, Leu8, Tyr5, Phe1 while Fd II had 99 residues of Trp1, Lys4, His1, Arg1, Asp18, Thr7, Ser6, Glu14, Pros, Gly5, Ala6, Gys5, Val6, Met1, Ile6, Leu8, Tyr4,Phe1. From the amino acid compositions, molecular weights were calculated to be about 10,500 for Fd I and 10,700 for Fd II. The amino terminals of both Fd I and Fd II were alanine. The carboxyl terminal sequence of Fd I was -Glu-Leu-Tyr and that of Fd II was -Glu-(Ser, Ala)-Leu-Ala. Fd I was more resistant against heat denaturation than Fd II.