Evidence for two nonidentical subunits of bacterioferritin from Azotobacter vinelandii

Abstract

The bacterioferritin from Azobacter vinelandii exhibits properties which in ferritins from other sources are attributed to the heteropolymeric nature of the holoprotein. The native bacterioferritin displayed multiple band on isoelectric focusing gels. On discontinuous sodium dodecyl sulfate-polyacrylamide gels, there were two subunit polypeptides of approximate M(r) 21,000 and 23,000. These molecular weights were corroborated by gel filtration experiments. Peptide maps produced by partial trypsin digestion and electrophoresis showed no detectable differences between the subunits. Similarities to well-characterized mammalian ferritins and apparent anomalies in two commonly applied electrophoretic procedures are discussed.