[Study of the topography of the nitrogenase active center by the electron microscopy method with the use of the electron density labels].

The electron microscopy method has been used for studying the topography of the active centre of the nitrogenase in combination with the method of electron density labels. The active centre has been shown to place on the nitrogenase macromolecule asymmetrically. The non-heme iron atoms of the nitrogenase active centre have been regularly packed and located on the macromolecule as a quadrangular cluster closely to the surface of subunits. Two free sulfhydryl groups of the ATP-site of the nitrogenase active centre are in close proximity to the cluster. ATP-site of the nitrogenase active centre containing these groups is located on the Fe-enzyme, while the main part of the iron-containing cluster is located on the Mo-Fe-enzyme.