PQQA IS NOT REQUIRED FOR BIOSYNTHESIS OF PYRROLOQUINOLINE QUINONE IN METHYLOBACTERIUM-EXTORQUENS AM1

Methylobacterium extorquens AM1 is a facultative methylotroph that oxi dizes methanol via the pyrroloquinoline quinone (PQQ)-linked enzyme me thanol dehydrogenase. In M. extorquens AM1 and other PQQ-synthesizing bacteria, several genes are involved in the synthesis of PQQ and one o f these, pqqA, has been proposed to encode a peptide precursor of PQQ In other PQQ-synthesizing bacteria. pqqA is required for PQQ productio n. In this study, it is shown that both deletion and insertion mutants of pqqA in M. extorquens AM1 grow normally on methanol and produce pQ Q. The level of PQQ production is reduced in the insertion mutant, but it is sufficient to allow normal growth on methanol. These results su ggest either that a different peptide in M. extorquens AM1 can substit ute for PqqA in pqqA mutants, or that PqqA-like peptides may not be ob ligatory precursors of PQQ. In addition, it is shown that the methanol oxidation transcriptional regulator gene, mxbM, is required for norma l methanol induction of PQQ synthesis.