The complete primary structure of Pseudomonas stutzeri strain ZoBell ferredoxin was determined by a combination of protease digestion, Edman degradation, and carboxypeptidase digestion and was: T F V V T D N C I K C K Y T D C V E V C P V D C F Y E G P N F L V I H P D E C I D C A L C E P E C P A Q A I F S E D E V P E D Q Q E F I E L N A D L A E V W P N I T E K K D A L A D A E E W D G V K D K L Q Y L E R.The calculated molecular weight was 12,110 excluding iron and sulfur atoms. The amino acid sequence was highly homologous to those of Azotobacter vinelandii and Pseudomonas ovalis ferredoxins. It showed, like the other two, a Tyr-Thr insertion between the second and third Cys, and extra Cys at position 24 and, compared to Clostridium- and Bacillus-type ferredoxins, an extended C-terminal sequence.