Isolation and properties of a ferredoxin from leaves of Sambucus racemosa L.

Abstract

Ferredoxin was isolated in good yield from leaves of Sambucus racemosa L. by the following procedure: (1) homogenization in buffered acetone-water (1:1v/v); (2) ion-exchange chromatography on several columns of DEAE-cellulose; and (3) purification by gel filtration with Sephadex G-75. The ultraviolet and visible spectrum showed maxima at 277, 331, 423, and 466 nm. The electron paramagnetic resonance spectrum was centered around g = 1.957. The protein sustained an initial photoreduction rate of 86 mumol NADP per milligram chlorophyll per hour. The amino acid composition was found to be Lys 5, His 2, Arg1, Asx11, Thr5, Ser7, Glx17, Pro6, Gly7, Ala6-7, Cys4, Val8, Ile5, Leu7, Tyr3, Phe2, and Trp1. The molecule had a molecular weight of 10 700 and contained two atoms of iron. The amino-terminal residue was alanine. These properties are highly similar to those of other angiosperm ferredoxins. Sambucus ferredoxin was found to be most closely related to that of Leucaena.

Interpretation of the difference index as a guide to protein sequence identity

“…Several other comparisons confirmed the agreement between the two methods, whether they were applied to small and closely similar proteins, such as the ferredoxins from Leucaena glauca (Benson & Yasunobu, 1969) and Sambucus racemosa L. (Altosaar, Bohm & Taylor, 1977), or to large and compositionally dissimilar proteins, such as the molybdenum-iron protein components of the nitrogenases from Azotobacter chroococcum and Clostridium pasteurianum (Yates & Planqub, 1975).…”