Characterization of a new type of molybdenum cofactor-mutant in cell cultures of Nicotiana tabacum

Involvement of chlA, E, M, and N loci in Escherichia coli molybdopterin biosynthesis

“…That conclusion was based primarily on the finding that chlAI extracts required higher levels of Mo (.40 mM) during nit-i reconstitution than did wild-type extracts (10 mM). A similar finding and interpretation have been reported for four allelic Nicotiana tabacum cnx mutants (45). We have confirmed that chlAI extracts have a higher Mo requirement than chl+ during crude nit-i reconstitution (31).…”

“…Reconstitution of nit-i has been extensively used to characterize possible Mpt-mutants in many species (3,11,44,45,47,68). However, even with the modification used here to obtain quantitative results, the potential for in vitro formation of active cofactor is present when crude extracts of nit-i and any other mutant are mixed.…”

Mcp1 Encodes the Molybdenum Cofactor Carrier Protein in Chlamydomonas reinhardtii and Participates in Protection, Binding, and Storage Functions of the Cofactor

“…Moco Binding-Moco binding experiments were performed using Moco extracted from 250ϫ diluted milk XO as described previously (10). Freshly isolated Moco (1 l) was incubated with 0.75 g of MocoCP for a defined time at room temperature.…”

“…This cofactor is very unstable in vitro, and molybdenum readily dissociates from the cofactor complex, converting irreversibly into an inactive form such that molybdate stabilizes Moco (9,10). Other sulfhydryl-protecting agents stabilize Moco (10,11), whereas sulfhydryl-reactive inhibitors prevent the reconstituting activity of the cofactor (12), indicating the participation of free sulfhydryl groups in the reconstitution process. Oxygen seems to be a major factor of free Moco inactivation, which might be especially dramatic in autotrophs because of the photosynthetic activity.…”

Molybdenum cofactor biosynthesis and deficiency

“…Nason et al [23] found that the reconstituting activity released from diverse Mo enzymes was very labile, with a lifetime of a few minutes, indicating the oxygen-sensitive nature of Moco. The need to include an excess of molybdate [25][26][27] into the reconstitution mixture indicated a strong tendency of Moco to lose Mo, while sulfhydryl reactive agents totally inhibited Moco activity in the nit-1 assay [26][27][28][29], thus pointing to the participation of sulfur in metal coordination. The elucidation of the chemical nature of Moco is mainly based on the pioneering work of Rajagopalan and co-workers [2].…”