Novel Dephosphotetrahydromethanopterin Biosynthesis Genes Discovered via Mutagenesis in Methylobacterium extorquens AM1

DOI: 10.1128/JB.187.7.2508-2512.2005

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FIG. 1.
Cluster of archaeal-type genes in M. extorquens AM1. Functions of genes shown as grey arrows are known. fhcA, -B, -C, and -D encode the four subunits of the formyltransferase-hydrolase complex (16), mptG encodes ribofuranosylaminobenzene phosphate synthase (18), mtdB encodes methylene-H₄MPT dehydrogenase (9), mch encodes methenyl-H₄MPT cyclohydrolase (17), and fae encodes formaldehyde-activating enzyme (22). The function of ORFY remains unknown. Functions of genes shown in hatched arrows are assessed in this study. Genes shown as open arrows, as well as mtdB, have no homologs among Archaea.
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FIG. 2.
Structures of H₄MPT and H₄MPT analogs discussed in this study.

TABLE 1.

Characteristics of genes and mutants involved in this study

Gene	COG/Pfam-predicted general function	Methanol MIC (mM)^a	Complementation for^b:		MDH test result	dH₄MPT test result^c
Gene	COG/Pfam-predicted general function	Methanol MIC (mM)^a	Growth	C₁ sensitivity	MDH test result	dH₄MPT test result^c
ORF5	Cofactor biosynthesis	0.09	−	+	+	−
ORF7	Cofactor biosynthesis	0.13	+	+	+	+
ORF9	C₅ ring cleavage	0.10	−	−	+	−
ORF17	Ribonucleotide isomerase	0.20	+	+	+	+
ORF19	Unknown	0.10	+	+	+	−
ORF20	Cofactor biosynthesis	0.10	+	+	+	−
ORF21	Kinase	0.09	−	+	−	−
ORF22	Unknown	0.09	−	+	Low	−

↵ a For comparison, the wild-type strain is not inhibited by 100 mM methanol.
↵ b +, positive; −, negative. Results of expressing a gene in trans, from a low-activity or a high-activity promoter, are shown.
↵ c +, dH₄MPT detected at or above the wild-type level of 64 μM dH₄MPT; −, dH₄MPT undetectable (detection limit, 3 μM dH₄MPT).