Table 1. Nomenclature of strains and proteins of A. vinelandii related to this work.

Strain	Strain designation	Source	Genotype	Designation of component 1*	Designation of component 2*
Mo-nitrogenase
WT		26	WT	Av1	Av2
DJ1143	AvDJ1143	21	nifB deletion, His-tagged MoFe protein	ΔnifB Av1
DJ1165	AvDJ1165	17	nifH deletion, His-tagged MoFe protein	ΔnifH Av1
DJ1165	AvDJ1165	This study	nifH deletion, His-tagged MoFe protein, preincubated with Av2 and MgATP	ΔnifHAv1′
V-nitrogenase
WT		27-29	WT	Av1v	Av2v
YM7A	AvYM7A	This study	nifB deletion, His-tagged VFe protein	ΔnifB Av1v

^*The component proteins of the Mo-nitrogenase are designated by the initials of the organism from which they are isolated and the Arabic numeral of the component. For example, the MoFe and Fe proteins of the Mo-nitrogenase of A. vinelandii are designated Av1 and Av2, respectively. This nomenclature is also applied to the V-nitrogenase, with the addition of a superscript V. Therefore, the VFe and Fe proteins of the V-nitrogenase of A. vinelandii are abbreviated as Av1^v and Av2^v, respectively.