Lac repressor binds as a tetramer to two operators.

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#Unit 6. System Physiology – Plant

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#Unit 6. System Physiology – Plant

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#Unit 6. System Physiology – Plant

N2 constitutes about 80% of the earth’s atmosphere, but the stability of its triple bond renders it inert and metabolically inaccessible to most organisms.

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#Unit 6. System Physiology – Plant

Diazotrophs are able to catalyze the enzymatic reduction of this compound to ammonia (NH3) using the enzyme nitrogenase

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#Unit 6. System Physiology – Plant

Nitrogenase is a complex consisting of the MoFe protein (dinitrogenase or component I) a heterotetramer, and the Fe protein (dinitrogenase reductase or component II) a homodimer.

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#Unit 6. System Physiology – Plant

Fe protein 

contains 2 identical subunits (dimer) – nif H

Each subunit has MW of 30 ~ 72 kD.

Each subunit contains an Fe-S cluster (4Fe and 4S2-).