Comparative studies on membrane proteins of Nitrobacter hamburgensis and Nitrobacter winogradskyi

Abstract The inner membranes (i.e. cytoplasmic and intracytoplasmic membranes, IM) of autotrophically, mixotrophically, and heterotrophically grown cells of Nitrobacter hamburgensis were characterized with respect to their nitrite oxidase activity, density, and protein pattern as revealed by two-dimensional gel electrophoresis. In contrast to the IM of heterotrophically grown cells, those of auto- and mixotrophically grown cells had a high nitrite oxidase activity, a higher density of 1.18 g · cm^?3, and the M_r values of the three typical major proteins were 32 000, 70 000, and 116 000, respectively. The 32-kDa protein contained haem c. The IM of mixotrophically grown cells of Nitrobacter winogradskyi were similar to those of N. hamburgensis with respect to the three major proteins, but differed in some other proteins.