Structure of Klebsiella pneumoniae Nitrogenase

Abstract

The 3D crystallographic structure of the nitrogenase MoFe protein was first determined for the protein from Azotobacter vinelandii (Av1) at 2.8 Å resolution and identified two unique metal-sulphur clusters viz the FeMoco centres and the P clusters (Kim, Rees 1992). This structure was later refined to 2.2 Å resolution (Chan et al, 1993). Analysis of the structure of the MoFe protein from Clostridium pasteurianum (Cpl) was consistent with the formulation of FeMoco as MoFe₇S₉. homocitrate but differed in the interpretation of the structure of the P clusters (Bolin et al, 1993). Rees’s group reported that the P clusters consisted of two Fe₄S₄ clusters bonded through a disulphide bridge at one corner whereas Bolin suggested that the two Fe₄S₄ cubanes shared a single sulphur atom at the corner to produce an Fe₈S₇ cluster. (Fig 1)