Characterization of an [Fe.sup.2}-dependent archael-specific GTP cyclohydrolase, MptA, from Methanocaldococcus jannaschii

The article describes the newly discovered [Fe.sup.2}-dependent archael-specific GTP cyclohydrolase, MptA, which is obtained from Methanocaldococcus jannaschii and catalyzes the first step in the biosynthesis of methanopterin. The analysis reveals that the mutation of conserved histidine residues, expected to be involved in such binding, reduces the enzymatic activity, but not the amount of bond iron.