Molecular weight and subunit structure of molybdoferredoxin from Clostridium pasteurianum W5

Abstract

1. 1. Molybdoferredoxin, a component of the nitrogenase system of Clostridium pasteurianum W5, has a molecular weight of between 160 000 to 190 000 as estimated by gel filtration. 2. 2. Sodium dodecyl sulfate-treated molybdoferredoxin gives two bands on electrophoresis, one of which has a molecular weight of 59 500 ± 1940 and the other a molecular weight of 50 700 ± 1950. Microdensitometer tracings of the two bands and estimation of their areas suggest that there is a ratio of two subunits of the heavier protein to one subunit of the lighter protein. This argues that the molecular weight of molybdoferredoxin is about 170 000 and it contains two 59 500 and one 50 700 subunits.