– The key enzymatic reactions in nitrogen fixation are catalyzed by the nitrogenase complex, which has 2 components: the iron protein and the molybdenum-iron protein. nifH1 Protein, Methanobacterium ivanovii, Recombinant (His & Myc) is expressed in E. coli expression system with N-10xHis and C-Myc tag. The predicted molecular weight is 37.4 kDa and the accession number is P51602.