Structure of a Cofactor-Deficient Nitrogenase MoFe Protein

摘要

One of the most complex biosynthetic processes in metallobiochemistry is the assembly of nitrogenase, the key enzyme in biological nitrogen fixation. We describe here the crystal structure of an iron-molybdenum cofactor-deficient form of the nitrognease MoFe protein, into which the cofactor is inserted in the final step of MoFe protein assembly. The MoFe protein fold as a heterotetramer containing two copies each of the homologus　αand β subunits. In this structure, one of the three αsubunit domains exhibits a substantially changed conformation, whereas the rest of the protein remains essentially unchanged. A predominantly positively charged funnel is revealed; this funnel is of sufficient Size to accommodate insertion of the negatively charged cofactor.