In vitro system for molybdopterin biosynthesis.

Journal Article (Journal Article)

A high-Mr fraction present in chl+ and chlA1 strains of Escherichia coli synthesizes molybdopterin (MPT) from the low-Mr fraction of several MPT-deficient mutants. Using this in vitro complementation as an assay, we have partially characterized the high-Mr fraction as a protein, termed MPT converting factor, of Mr 45,000, distinguishable from the Mo cofactor carrier protein of similar Mr by its absolute requirement for the low-Mr fraction of a non-chlA1 mutant in the nit-1 reconstitution assay. MPT converting factor was rapidly inactivated in the absence of a reduced sulfhydryl compound. Anaerobic incubation of MPT converting factor with trypsin destroyed its activity. High-performance liquid chromatographic analysis of alkaline KMnO4 oxidation products demonstrated that the factor did not contain any bound pterin. Since mutants lacking MPT converting factor are not auxotrophs for folate or riboflavin, the factor appears to be distinct from known pteridine biosynthetic enzymes in E. coli. We have partially purified and characterized the low-Mr fractions as probable MPT precursors. Several distinct precursors were separable by high-performance liquid chromatography. Like MPT activity, precursor activity was oxygen sensitive. Precursor activity was not correlated with levels of L-threo-neopterin, a major pterin of unknown function in E. coli. Precursor activity was correlated with levels of a new 6-alkylpterin, compound Z, produced by acidic iodine oxidation. Compound Z has the properties expected of an oxidized MPT precursor.

Full Text

Duke Authors

Cited Authors

  • Johnson, ME; Rajagopalan, KV

Published Date

  • January 1987

Published In

Volume / Issue

  • 169 / 1

Start / End Page

  • 110 - 116

PubMed ID

  • 3539912

Pubmed Central ID

  • PMC211741

International Standard Serial Number (ISSN)

  • 0021-9193

Digital Object Identifier (DOI)

  • 10.1128/jb.169.1.110-116.1987


  • eng

Conference Location

  • United States