Fig. 1.

Biosynthesis and structure of the nickel-pincer nucleotide (NPN) cofactor. LarB catalyzes both pyridinium ring C5 carboxylation of nicotinic acid adenine dinucleotide (NaAD) and the hydrolysis of the phosphoanhydride, releasing AMP, to produce pyridinium-3,5-biscarboxylic acid (P2CMN). LarE uses ATP to activate the pyridinium ring carboxyl groups of P2CMN by adenylylation, and then transfers a cysteinyl sulfur atom to this substrate to release AMP and produce dehydroalanine. Two molecules of LarE are needed to produce each molecule of pyridinium-3,5-bisthiocarboxylic acid mononucleotide (P2TMN). LarC transfers a protein-bound nickel ion into P2TMN in a CTP-driven reaction producing the NPN cofactor. The metallacycle generated by this reaction is highlighted by bold lines.