Physicochemical Properties of Ferredoxin from Chlamydomonas reinhardii

Abstract

Ferredoxin from Chlamydomonas reinhardii has been purified to electrophoretic homogeneity by an easy and fast procedure with a high yield (25-30 mg/250 g wet weight of cells). An average molecular weight of 11800 was calculated from sedimentation coefficient (1.70 S) and Stokes radius (1.75 nm) data, sodium dodecyl sulfate-electrophoresis, andamino acid composition. Absorption spectrum showed maxima at 276, 330, 420 and 460 nm in the oxidized form, with an absorptionratio {A 420 A276) of 0.54 and an extinction coefficient of 8.38 mM-1.c m-1 at 420 nm. Reduced ferredoxin showed a single peak at 276 nm with shoulders at 284, 310, 390, 469 and 537 nm and at liquid helium temperatures gave EPR signals at g = 1.877, 1.951 and 2.045. The protein has an isoelectric point of 3.30, andone (2F e -2S)-cluster per m oleculewith a midpoint potential, at pH 7.5, o f -410 m V (n = l). The molecule of C. reinhardii ferredoxin consists of 95-99 amino acid residues which includes the full complement of amino acids, being alaninethe most abundant. © 1985, Walter de Gruyter. All rights reserved.